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AFWL-TR-70-176 AFWL-TR- 70-176

BASIS FOR THE DEVELOPMENT OF A SOIL STABILIZATION INDEX SYSTEM

V /

Jon A. Epps, Ph.D.

Wayne A. Dunlap, Ph.D. Bob M. Galloway

Texas A A M University

TECHNICAL REPORT NO. AFWL-TR-70-176

December 1971

AIR FORCE WEAPONS LABORATORY Air Force Systems Command

Kirtland Air Force Bate New Mexico

D DC

RtproducMl by

NATIONAL TECHNICAL INFORMATION SERVICE

Springfield, V». 22151

Approved for public release; distribution unlimited.

<ia\ ^

. ■

■■ . ■•

UNCLASSIFIED Security e^B»iflc«tion

DOCUMENT CONTROL DATA R&D (S»eurlly clmuHlemllon ot tltl», body ol abtlncl end Indexing annotation must bt anlend when the ovetmll r»potl I» elatmlllmd)

I ORIGINATING ACTIVITV (Corporate author)

Texas A&M University College Station, Texas 77843

2«. REPORT SECURITV CLASSIFICATION

UNCLASSIFIED 2b. GROUP

3 REPORT TITLE

BASIS FOR THE DEVELOPMENT OF A SOIL STABILIZATION INDEX SYSTEM

4. DESCRIPTIVE NOTES (Type ol report and Inclusive dalee)

Nnvemher _1969-Deceihber 1970 S AUTHORISI (Flraf name, middle Initial, laal name)

Jöh A. Epps, Ph.D.; Wayne A. Dunlap, Ph.D.; Bob M. Gallaway

6 REPORT DATE

December 1971 7«. TOTAL NO. OF PAGES

290 7b. NO. OF REFS

104 »a. CONTRACT OR GRANT NO

b. PROJECT NO

c Task No.

d.

F29601-70-C-0008

683M

4.9.001

9a. ORIGINATOR'S REPORT NUMBER(S)

AFWL-TR-70-176

»6. OTHER REPORT NOISt (Any other numbere thai may be aeil0»ad thle report)

10 DISTRIBUTION STATEMENT


II SUPPLEMENTARY NOTES 12. SPONSORING MILITARY ACTIVITV

AIWL (DEZ) Kirtland AFB, NM 87117

IS ABSTRACT

(Distribution Limitation Statement A) ^A soil stabilization index system has been developed to aid military engineers in

selecting the appropriate type and amount of soil stabilizer to use in pavement construction. This report contains the index system and the basis for its development. The index system is entered with easily determined soil properties and flow charts are followed to arrive at the most suitable stabilizer. Subsystems containing appropriate tests are used to determine specific amounts of stabilizers. Use factors, construction factors, and environmental factors are also considered in the decision- making process. Although the index system was based on a comprehensive review of published informaxion and personal opinions of acknowledged experts in the soil stabilization field, there were often conflicting viewpoints necessitating validation of the proposed system. A plan for laboratory validation of the index system is outlined.

DD 1^.1473 UNCLASSIFIED Security Classification

,„««Mr*i*wa»*'V.'V*«* .jr^f^^T i ■

AFWL-TR-70-176

AIR FORCE WEAPONS LABORATORY Air Force Systems Command Klrtland Air Force Base

New Mexico 87117 M

When US Government drawings, specifications, or other data are used for any purpose other than a definitely related Government procurement operation, the Government thereby Incurs no responsibility nor any obligation whatsoever, and the fact that the Government may have formulated, furnished, or in any way supplied the said drawings, specifications, or other data, Is not to be regarded by implication or otherwise, as in any manner licensing the holder or any other person or corporation, or conveying any rights or permission to manufacture, use, or sell any patented invention that may in any way be related thereto.

This report is made available for study with the understanding that proprietary interests in and relating thereto will not be impaired. In case of apparent conflict or any other questions between the Government's rights and those of others, notify the Judge Advocate, Air Force Systems Command, Andrews Air Force Base, Washington, DC 20331.

DO NOT RETURN THIS COPY. RETAIN OR DESTROY.

s? immism-o 14

KEV WONOS

Civil engineering Soil stabilization Soil cement stabilization Bituminous soil stabilization Lime soil stabilization Compaction Airfield pavements Pavements

LINK c

UNCLASSIFIED Security Classification

AFWL-TR-70-176

BASIS FOR THE DEVELOPMENT OF

A SOIL STABILIZATION INDEX SYSTEM

Jon A. Epps, Ph.D. Wayne A. Dunlap, Ph.D.

Bob M. Gallaway Texas A&M University

TECHNICAL REPORT NO. AFWL-TR-70-176


ABSTRACT

A soll stabilization Index system has been developed to aid military

engineers In selecting the appropriate type and amount of soil stabilizer to

use In pavement construction. This report contains the Index system and the

basis for Its development. The Index system Is entered with easily determined

soil properties and flow charts are followed to arrive at the most suitable

stabilizer. Subsystems containing appropriate tests are used to determine

specific amounts of stabilizers. Use factors, construction factors and

environmental factors are also considered In the decision making process.

Although the Index system was based on a comprehensive review of published

Information and personal opinions of acknowledged experts In the soil

stabilization field, there were often conflicting viewpoints necessitating

validation of the proposed system. A plan for laboratory validation of the

Index system Is outlined.

(Distribution Limitation Statement A)

111/lv

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AFWL-TRV70-176

FOREWORD

This report was prepared by the Texas A&M University, College Station, Texas, under Contract F29601-70-C-0008. The research was performed under Program Element 63723F, Project 683M, Task 4.9.001.

Inclusive dates of research were November 1969 through December 1970. The report was submitted 26 November 1971 by the Air Force Weapons Laboratory Project Officer, Captain Phil V. Compton (DEZ). The previous project officer was Captain David D. Currin (DEZ).

This technical report has been reviewed and is approved.

PHIL V. COMPTON Captain, USAF Project Officer

I «

■V ^RENCE E.VTESKE/ WILLIAM B. LlJbDICOET

Lt Colonel, USAF Colonel, USAF Chief, Aerospace Facilities Chief, Civil Engineering Research

Branch Division

f

CONTENTS

Section Page

I INTRODUCTION 1

Background 1 Scope of Report 3

II THE AIR FORCE STABILIZATION SYSTEM A

Objectives A Processes of Soil Stabilization 5 Air Force Soli Stabilization System 6

III SELECTION OF CRITERIA FOR THE BASIS OF THE CHEMICAL SOIL STABILIZATION INDEX SYSTEM 13

Introduction 13 Existing Guides for Selecting Stabilizing Agents 16 Criteria for Lime Stabilization 18 Criteria for Cement Stabilization 21 Criteria for Bituminous Stabilization 21 Criteria for Combination Stabilization 32 Summary of Criteria for Selecting Stabilizing Agents 34

IV DESIGN SUBSYSTEM FOR BITUMINOUS STABILIZATION 45

Introduction 45 Selection of the Type of Bitumen ^5

/ Selection of the Quantity of Bitumen 54 Methods of Evaluating Bitumen-Soil Mixtures 70 Summary of Criteria for Bituminous Stabilization Subsystem 71

V DESIGN SUBSYSTEM FOR PORTLAND CEMENT STABILIZATION 81

Introduction 81 Selection of Appropriate Soils 81 Selection of the Type of Cement 84 Selection of the Quantity of Cement 84 Methods of Evaluating Soil-Cement Mixtures 88 Summary of Criteria for Cement Stabilization Subsystem 92

t

,. ■

CONTENTS CCONT'D)

Section Page

VI DESIGN SUBSYSTEM FOR LIME STABILIZATION 103

Introduction 103 Selection of the Type of Lime 103 Selection of Appropriate Soils 105 Selection of the Quantity of Lime 108 Methods of Evaluating Soil-Cement Mixtures 108 Summary of Criteria for Cement Stabilization Subsystem 110

VII SELECTION OF CRITERIA FOR MECHANICAL STABILIZATION 118

Introduction 118 Compaction Requirements 122 Blending 125 Special Considerations 125

VIII CONSTRUCTION FACTORS 131

Introduction 131 Traveling Mixers 132 Related Stabilization Equipment 135 Stationary Mixing Plants 135 Equipment Used for Expedient Soil Stabilization 137 Equipment Requirements or Limitations for Particular Types of Stabilization 137 Sununary of Construction Requirements and Limitations 141

IX ENVIRONMENTAL FACTORS 143

Introduction 143 Sources and Types of Available Environmental Information 143 Influence of Temperature and Rainfall on Soil Stabilization 144 Summary of Environmental Requirements and Limitations 151

X RECOMMENDATIONS FOR FUTURE RESEARCH 152

Introduction 152 General Areas of Recommended Research 153 Specific Research Recommendations Related to Validation of the Index System 161 Proposed Program for Phase II Research 162

vl

■

CONTENTS (CONT'D)

Appendix Page

A Expedient Subgrade Stabilization System 167

B Expedient Base Course Stabilization System 183

C Nonexpedlent Subgrade Stabilization System 200

D Nonexpedlent Base Course Stabilization System 216

E Rapid Test Procedures for Expedient Construction Operations Using Soil-Cement Stabilization 234

F pH Test on Soil-Cement Mixtures 237

G Determination of Sulfate In Soils 240

H Selection of Cement Content for Cement Stabilized Sandy-Soil 248

I Selection of Cement Content for Base Course Soil-Cement Mixtures 255

' J pH Tests to Determine Lime Requirements for Lime Stabilization 260

REFERENCES 263 /

ACKNOWLEDGMENTS 270

vll

FIGURES

Figure Page

1 The Air Force Soil Stabilization System 7

2 Gradation Triangle for Aid in Selecting a Commercial Stabilizing Agent 17

3 Suggested Stabilizing Admixtures Suitable for Use With Soils, as Indicated by Plasticity Index and Amount Passing No. 200 Sieve 19

4 Approximate Interrelationships of Soil Classifications and Bearing Values 20

5 Selection of Stabilizer for Expedient Subgrade Construction 38

6 Selection of Stabilizer for Expedient Base Construction 39

7 Selection of Stabilizer for Nonexpedient Subgrade Construction 40

8 Selection of Stabilizer for Nonexpedient Base Construction 41

9 Selection of Type of Cutback for Stabilization 50

10 Classification of Aggregates 52

11 Approximate Effective Range of Catlonic and Anionic Emulsions on Various Types of Aggregates 53

12 Subsystem for Expedient Subgrade Stabilization With Bituminous Materials 77

13 Subsystem for Expedient Base Course Stabilization With Bituminous Materials 78

14 Subsystem for Nonexpedient Subgrade Stabilization With Bituminous Materials 79

vlii

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Figure Page

15 Subsystem for Nonexpedient Base Course Stabilization With Bituminous Materials 80

16 Effect of Soll pH Value on the Unconflned Corapresslve Strength of Soil Cement Mixtures 83

17 Soil-Cement Laboratory Testing Methods 90

18 Flow Diagram for Short-cut Method Using Surface Area to Determine Cement Requirements 91

19 Minimum 7-day Compresslve Strengths Required for Soil- Cement Mixtures Containing Material Retained on the No. A Sieve 95

20 Minimum 7-day Compresslve Strengths Required for Soil- Cement Mixtures Not Containing Material Retained on the No. 4 Sieve ' 96

21 Subsystem for Expedient Subgrade Stabilization With Portland Cement 99

22 Subsystem for Expedient Base Course Stabilization With Portland Cement 100

23 Subsystem for Nonexpedient Subgrade Stabilization With Cement 101

24 Subsystem for Nonexpedient Base Course Stabilization With Cement 102

25 Subsystem for Expedient Subgrade Stabilization With Lime 114

26 Subsystem for Expedient Base Course Stabilization With Lime 115

27 Subsystem for Nonexpedient Subgrade Stabilization With Lime 116

28 Subsystem for Nonexpedient Base Course Stabilization With Lime 117

29 Temperature-Viscosity of Liquid Asphalt 148

30 A Simplified Pavement Design System With Emphasis on Stabilized Materials 155

ix

Figure Page

31 Selection of Stabilizer for Expedient Subgrade Construction 168

32 Subsystem for Expedient Subgrade Stabilization With Bituminous Materials 169

33 Subsystem for Expedient Subgrade Stabilization With Portland Cement 170

34 Subsystem for Expedient Subgrade Stabilization With Lime 171



37 Approximate Effective Range of Cationlc and Anionic Emulsions on Various Types of Aggregates 174

38 Selection of Stabilizer for Expedient Base Construction 184

39 Subsystem for Expedient Base Course Stabilization With Bituminous Materials 185

40 Subsystem for Expedient Base Course Stabilization With Portland Cement 186

41 Subsystem for Expedient Base Course Stabilization With Lime 187



44 Approximate Effective Range of Cationlc and Anionic Emulsions on Various Types of Aggregate" 190

45 Selection of Stabilizer for Nonexpedient Subgrade Construction 201

46 Subsystem for Nonexpedient Subgrade Stabilization With Bituminous Materials 202

47 Subsystem for Nonexpedient Subgrade Stabilization With Cement 203

■';«*«*»»™»»_„

Figure Page

48 Subsystem for Nonexpedlent Subgrade Stabilization With Lime 204



51 Approximate Effective Range of Cationic and Anionic Emulsions on Various Types of Aggregates 207

52 Selection of Stabilizer for Nonexpedlent Base Construction 217

53 Subsystem for Nonexpedlent Base Course Stabilization With Bituminous Materials 218

54 Subsystem for Nonexpedlent Base Course Stabilization With Cement 219

55 Subsystem for Nonexpedlent Base Course Stabilization With Lime 220



58 Approximate Effective Range of Cationic and Anionic Emulsions on Various Types of Aggregates 223

59 Example Standard Curve for Spectrophotometer 247

xi

TABLES

Table Page

1 Most Effective Stabilization Methods for Use With Different Soil Types 14

2 Soil Types and Stabilization Methods Which Appear Best Suited for Specific Applications 15

3 Grading Limits for Cement Stabilization of Well Graded Granular Materials 22

4 Atterberg Limit Requirements for Cement Stabilized Soils 22

5 Types of Soil Bitumen and Characteristics of Soils Empirically Found Suitable for Their Manufacture 24

6 Grading and Plasticity Requirements for Soil-Bitumen Mixtures 25

7 Engineering Properties of Materials Suitable for Bituminous Stabilization 2^

8 Grading, Plasticity and Abrasion Requirements for Soils Suitable for Emulsified Asphalt Treated Base Course 27

9 Typical Aggregates Suitable for Treatment With Bitumuls Emulsified Asphalts 29

10 Guidelines for Emulsified Asphalt Stabilization 30

11 Grading Requirements for Sandy and Semi-processed Material 30

12 Typical Asphalt Cement Treated Base Course Requirement 31

13 Aggregate Gradation Specification Limits for Bituminous Pavements 33

xil

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Table Page

14 Environmental and Construction Precautions for Lime Stabilization 42

15 Environmental and Construction Precautions for Cement Stabilization 43

16 Environmental and Construction Precautions for Bituminous Stabilization 44

17 Suitable Types of Bitumen for Stabilization 46

18 Suitable Types of Bituminous Materials 48

19 Selection of Type of Emulsified Asphalt for Stabilization 49

20 Chevron Asphalt Company Product Specifications for Bitumuls Emulsified Asphalt Mixing Grades 51

21 Specifications for Asphalt Cement 55

22 Specifications for Cutback Asphalts 56

23 Specifications for Emulsions 57

24 Emulsified Asphalt Requirement 61

25 Design Methods and Criteria for Coarse Aggregate Hot Mix Base Courses 62

26 Criteria for Determination of Optimum Bitumen Content 63

27 Bitumen Content and Penetration Grade of Asphalt for Various Temperature Index Ranges 65

28 Mixture Design Criteria 66

29 Marshall Mix Design Criteria for Asphalt Cement Treated Base Course 67

30 Marshall Mix Design Criteria for Cutback and Emulsified Asphalt Mixtures 67

31 Hveem Mix Design Criteria Emulsified Asphalt Mixtures 69

xiii

Table Page

32 Selection of a Suitable Type of Bitumen for Soil Stabilization Purposes 69

33 Selection of Asphalt Cement Content for Expedient Base Course Construction 72

34 Determination of Asphalt Grade for Base Course Stabilization 72

35 Determination of Quantity of Cutback Asphalt 73

36 Specifications for Portland Cement 85

37 Cement Requirements for Various Soils 86

38 Average Cement Requirements of B and C Horizon Sandy Soils 87

39 Average Cement Requirements of B and C Horizon Sllty Clayey Soils 87

40 Average Cement Requirements of Miscellaneous Materials 89

41 Portland Cement Association Criteria for Soil-Cement Mixtures Used in Base Courses 93

42 Ranges of Unconflned CompressIve Strengths of Soil-Cement 94

43 Unconflned Compresslve Strength Criteria for Soil- Cement Mixtures 94

44 Specifications for Hydrated Lime 106

45 Approximate Lime Contents 109

46 Tentative Lime-Soil Mixture Compresslve Strength Requirements 111

47 Characteristics Pertinent to Roads and Airfields 120

48 Compaction Requirements 123

49 Grading and Atterberg Limits for Select and Subbase Material 126

xiv

-.... ■.,...-. ■ -i-i . , .-

Table Page

50 Desirable Gradation for Crushed Rock, Gravel or Slag, and Uncrushed Sandy and Gravel Aggregate for Base Courses and for Mechanical Stabilization 127

51 Atterberg Limit Requirements for Blending 127

52 Frost Susceptible Soils With Relation to Pavements 130

53 Mixing and Spraying Temperatures for Various Grades of Liquid Asphalt 147

54 Environmental and Construction Precautions for Bituminous Stabilization in Expedient Subgrades 175

55 Environmental and Construction Precautions for Cement Stabilization In Expedient Subgrades 176

56 Environmental and Construction Precautions for Lime Stabilization In Expedient Subgrades 177






62 Approximate Lime Contents 182

63 Environmental and Construction Precautions for Bituminous Stabilization in Expedient Base Courses 191

64 Environmental and Construction Precautions for Cement Stabilization In Expedient Base Courses 192

65 Environmental and Construction Precautions for Lime Stabilization In Expedient Base Courses 193


xv

Table Page


68 Determination of Asphalt Grade for Base Course Stabilization 1P6





73 Tentative Lime-Soil Mixture Compressive Strength Requirements 199

74 Environmental and Construction Precautions for Bituminous Stabilization in Nonexpedient Subgrades 208

75 Environmental and Construction Precautions for Cement Stabilization in Nonexpedient Subgrades 209

76 Environmental and Construction Precautions for Lime Stabilization in Nonexpedient Subgrades 210







83 Environmental and Construction Precautions for Bituminous Stabilization in Nonexpedient Base Courses 224

xvi

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Table Page

84 Environmental and Construction Precautions for Cement Stabilization In Nonexpedlent Base Courses 225

85 Environmental and Construction Precautions for Lime Stabilization in Nonexpedlent Base Courses 226



88 Determination of Asphalt Grade for Base Course Stabilization 229


90 Mixture Design Criteria 230




94 Portland Cement Association Criteria for Soil-Cement Mixtures Used in Base Courses 232


xvii/xviii

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SECTION I

INTRODUCTION

1. Background

The United States Air Force currently owns over 500 million square

yards of pavement. Runways, taxiways and parking aprons alone have a

total surface area equivalent to a 200 foot wide runway stretching from

the state of Washington to the southern tip of Florida.

These pavements represent nearly 40 percent of all funds spent for

support facilities, and nearly 400 million dollars are spent annually in

maintaining these facilities. This figure would be significantly increased

if it included pavements owned by other branches of the United States

armed forces.

To effectively cope with this substantial pavement inventory, military

engineers involved in maintaining, strengthening and reconstructing existing

pavements, as well as those constructing new pavements, must be aware of any

and all construction alternatives available to reduce construction time,

initial cost and maintenance costs. The attractive engineering and

economic benefits of soil stabilization make it important that this alter-

native be considered.

Stabilizing soils to improve their engineering properties is not new -

it has been practiced for centuries. However, chemical soil stabilization

did not gain widespread acceptance in road and runway construction until

after World War II. With increasing use of stabilization processes during

1

the last 2 1/2 decades, voluminous research results have been published

by highway departments, groups representing producers of stabilizing

materials, and various research organizations, to name a few.

Even though a wealth of technical information and data now exists on

soil stabilization, there has been no significant attempt to correlate this

information into a useable system which would classify or index soils with

respect to a) their suitability for stabilization, and b) the most appro-

priate type and amount of stabilizer to use. To further complicate matters

the available data often favor a particular product, and do not include

the worldwide variety of soils which military engineers are likely to en-

counter. This creates a dilemma for the military engineer, who often

lacks extensive training in soil stabilization, who lacks time and equipment

for sophisticated evaluation tests, and who often works in areas where

there are no previous records regarding feasibility of soil stabilization.

To alleviate this problem, the U. S. Air Force Weapons Laboratory (AFWL)

has embarked on an extensive research program covering many aspects of soil

stabilization. Initial research involved the determination of the basic

physico-chemical properties of soils which influence their response to

stabilization. Next, the Air Force sponsored a research project at Texas

A&M University aimed at developing a soil stabilization index system. The

ultimate objective of the index system is to determine a soil's suitability

for stabilization and to indicate the most appropriate type and amount of

stabilizer. The Index system should contain all useful knowledge on soil

stabilization arranged in such a form that it can be effectively used even

by engineers who are not trained in stabilization techniques. Of necessity,

the stabilization index system should not only consider those relevant soil

properties that influence soil stabilization, but should also take into

2

. --..., .;;■.■,.

account such factors as:

■ a. urgency of construction

b. location of the stabilized layer In the pavement

c. type of construction equipment available or needed

d. Influence of the environment on the stabilized layer

2. Scope of Report

It was specified that the soil stabilization Index system be developed

In two consecutive phases: Phase I was to be the establishment of the Index

system based on existing knowledge; Phase II was to be devoted to filling In

the voids In knowledge and validating the Index system by appropriate

testing.

This report Is concerned primarily with Phase I of the research. In

particular, this report contains the Index system and detailed justification

for the establishment of the system. It Is not Intended as a complete text

or manual, although, by the use of appropriate appendices. It may serve as

such.

During the accomplishment of Phase I of the research, many gaps In

knowledge were Identified which will reduce the reliability of the Index

system for use In the field. In this report the more critical gaps have

been Identified for study In Phase II of the research program. In addition,

a test program for validation of the Index system Is outlined.

Finally, several comments and recommendations are made pertaining to

the overall Air Force soil stabilization program. For the most part, this

information was also uncovered during accomplishment of Phase I.

SECTION II

THE AIR FORCE STABILIZATION SYSTEM

1. Objectives

One of the Air Force objectives Is to develop a systematic approach to

soil stabilization. When stabilization is used in a structural element of a

road or runway, it then encompasses the larger overall problem of pavement

design. It is not within the scope of this project to consider the pavement

design problem as such. However, a brief discussion of how stabilization

Interacts with pavement design is warranted.

An engineer faced with designing a pavement must first assess the load-

carrying capacity of the existing subgrade. The Air Force presently specifies

the CBR method of strength determination and uses this as a design method also.

Depending on the subgrade CBR, it can be determined how much overlying material

of higher quality must be used based on the type of traffic anticipated and

the life of the facility. This is basically a structural design problem, but

there may be other overriding factors - such as frost penetration - that will

Influence the thickness of overlying material.

At this point the engineer may consider stabilization. Whether to

stabilize the subgrade, the overlying material, or both, is a decision which

must be made. The military engineer must base his decision on many factors

including economy, availability of stabilizer and speed of construction. It

is here that the index system should assist the engineer. He should be able

to uae the index system as a guide to tell him what kind of stabilization to

4

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use and how much stabilizer he should use. Certain soils are not amenable

to stabilization and the index system should be capable of relaying this

information to the engineer. Other circumstances, e.g., climatic conditions,

lack of appropriate equipment, etc., may also rule out the possibility of

stabilization. Again, the index system should provide this Information.

However, the engineer should not be under the illusion that the index system,

in its present state of development, will provide design curves or other

Information of a structural design nature.

It is of utmost importance for the engineer to realize that the index

system is not a substitute for proper pavement design and that stabilization

is not a panacea for all pavement problems.

2. Processes of Soil Stabilization

Stabilization has been defined by Lambe (1)* as "the alteration of any

property of a soil to improve its engineering performance."

In recent years, the term modified has been used to indicate that gen-

eral soil properties have been improved without appreciable gains in strength,

whereas, stabilized has been reserved for cases where definite strength gains

are apparent. Although the term, modified, has not been universally accepted

(some engineers consider that an improvement in any characteristic, not

necessarily strength, constitutes stabilization), nevertheless, it is a

convenient definition to use and will be adopted in this report.

The primary stabilization methods are:

a. chemical stabilization

b. mechanical stabilization

*Number8 In parenthesis refer to References,

5

Öiemiaal stabilization, as the name implies, is the use of certain

chemical additives which are mixed into the soil to change the surface

molecular properties of the soil grains and, in some cases, to cement the

grains together resulting in strength Increases.

By far the largest volume of chemical stabilizers used throughout the

world are lime, cement and bitumens. Many other additives have been used,

some by themselves and some in conjunction with the three major ones listed

above. However, none of the many other stabilizers available have gained

universal acceptance and significant background information on their ap-

plicability is lacking. Thus, the index system at present will be concerned

only with the three major stabilizers, i.e., lime, cement and bitumens.

Medhaniaal stabilization may be accomplished by:

a. changing the gradation of the soil by the addition or

removal of particles

b. denslfying or compacting the soil

Soil compaction represents one of the most economical methods of stabilization.

In addition to its separate use, proper compaction is also required with soils

which have been chemically stabilized.

3. Air Force Soil Stabilization System

The overall systematic approach to the Air Force Soil Stabilization

Index System is shown in Figure 1. The development of this general scheme is

discussed below.

a. Type of Stabilization

When stabilization is to be used, it is then necessary to decide

whether mechanical stabilization alone will suffice, or whether it will

be necessary to utilize chemical stabilization. In addition to the

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pavement design aspects which must be considered, the engineer must

often weigh the economic gain obtained by mechanical stabilization

against that obtained by the addition of chemicals. From the military

aspect, time of construction may well override all other factors and

could be the sole reason for choosing one stabilization method over

another.

b. Use Factors

To be of most benefit, the Index system should recognize the two

significantly different uses for which It may be applied, i.e., Zone of

Interior construction and Theater of Operations construction. More

Importantly, under the present mobility concept of the Air Force, It

should be particularly suitable for hasty, forward airfield construction.

For this reason, the index system was divided into two construction

categories as follows (refer to Figure 1):

1. Expedient construction

2. Nonexpedient construction

Expedient is considered to be a short life, high risk situation in which

a limited construction and materials testing capability exists, and time

is of the essence. Nonexpedient is considered to be all other situations,

The tests used for establishing type and amount of stabilizer used in

expedient operations are the rapid, unsophisticated type, whereas the

more conventional tests are utilized in nonexpedient construction.

In certain nonexpedient, permanent construction situations (such as

might occur in the Zone of Interior) there is usually an unlimited

testing capability. Then, it may be desirable to consider chemical

stabilizers other than those presently considered In the index system

and conduct a more thorough laboratory evaluation. In such a situation,

8

the Index system will provide a starting point for the investigation.

Figure 1 shows another way in which use factors are entered into

the index system by specifying diffetent subsystems for subgnde md

base course stabilization. Subbases are not considered, but they may

fall either in the subgrade or base course subsystems depending on the

material type and desired strength characteristics.

It should be noted that the index system is presently limited to

stabilization for structural elements of roads and runways. It does

not include, for example, use of dust palliatives, erosion control, etc.

c. Basic Soil Parameters

These are the soil properties that influence the response of the

soil to stabilization. They are not shown directly on Figure 1, but

they enter into each of the subsystems which are discussed later. Un-

doubtedly, all of the parameters that influence stabilization are not

included and, in fact, they may never be known.* However, those in-

cluded are considered to be the most important with the present state of

knowledge and are among the easier parameters to obtain. They are:

1. Gradation, particularly the percent finer than 0.074 mm

(#200 sieve), 0.05 mm and 0.005 mm

2. Plasticity index

3. pH

4. Sulfate content

5. Organic content

*The work referred to in Section I regarding basic physico-chemical properties was not completed at the time this report was written. Pre- liminary indications are that most of them are included in one form or another.

,«.■•

Other Important parameters are expected to be forthcoming, and they will

be Incorporated Into the Index system as seen fit.

d. Environmental Factors

These are factors that might Influence the ultimate suitability and

durability of the stabilized soil. Again, they are not shown directly

In Figure 1, but are Included In the various subsystems. They are based

primarily on cllmatologlcal effects and not on the total environment

(which might also include such factors as wheel load and number of

repetitions). Both rainfall and temperature must be considered since

either can significantly influence the type and amount of stabilizer

used.

e. Construction Factors

Military engineers faced with hasty construction In the Theater of

Operations usually are faced with limited equipment also. Knowledge of

the type of equipment required for a certain stabilization task may

prove to be a valuable planning tool, not only In anticipating the type

of equipment necessary to perform a stabilization task, but also In

eliminating the use of a particular stabilizer If adequate equipment

and time are not available.

f. Pavement Design

As discussed earlier, an Important aspect of soil stabilization

Involves the design of the pavement cross section using stabilized

materials. Under the present CBR design scheme, this is a fairly

straightforward prncos^ If mechanical stabilization Is used, there

being no change in the basic design process. However, if chemical

stabilization is used, the problem becomes more complex. Not only do

the various use factors, environmental factors and construction factors

10

enter into play, but there is also the problem of evaluating the

physical characteristics of the stabilized material. Thus, there is a

continual interchange between pavement design and the total soil

stabilization index system.

g. Field Performance Requirements for Stabilized Soils

The desired performance of the stabilized soils must be established

by the Air Force. In most cases, this will be developed based on

anticipated life of the structure and allowable time for construction.

Examples of this information include the recently developed mobility

concepts and various other operational requirements which have been

developed by the Air Force,

h. Field Evaluation

The verification of the index system for soil stabilization must

ultimately come from the user, i.e., the Aii Force and its military

partners. On pavement projects where stabilization has been used,

adequate construction records and follow-up evaluations will be

absolutely necessary to verify the adequacy of the stabilized sections.

Continual evaluations of stabilized sections which are already in

place (such as the work being done by the Corps of Engineers at

the Waterways Experiment Station) will also aid in evaluating the

ultimate performance of the index system.

The remainder of this report is devoted to the development and justi-

fication of the soil stabilization index system. Greatest emphasis is

placed on development of systems and subsystems for chemical stabilization,

since it is here that the greatest confusion exists. Detailed systems and

subsystems for mechanical stabilization, which, in reality, represent the

11

«iiiMi—iiniinir'iBMc.- -

more common approach to the problem, are not presented. However, the

Information necessary to make an engineering judgment as to whether

chemical or mechanical stabilization should be used Is presented, and

guidelines to Insure the success of a mechanical stabilization program

are also presented In the appropriate places In the report. It Is antici-

pated that eventually It will be possible to provide subsystems for the

full range of mechanical stabilization procedures.

12

■■.-■/■,. -,, ,„

SECTION III

SELECTION OF CRITERIA FOR THE BASIS OF

THE CHEMICAL SOIL STABILIZATION INDEX SYSTEM

1. Introduction

This section of the report will present criteria for the basis of the

chemical soil stabilization system whereas Section VII will present criteria

for the mechanical stabilization system. Criteria will be reviewed which

define the particular types of soils which will most readily be stabilized

by each stabilizer (lime, cement and bituminous materials), and further, will

allow the engineer to determine the amount of stabilizer that is required to

provide the specified Improvement.

Several general guides have been published which assist the engineer in

the proper selection of a stabilizer for a particular soil. For example,

Air Force Manual AFM 88-51 (2) contains information which suggests that lime

is a more appropriate stabilizer for highly plastic clay soils while asphalt

should be used only for the coarse and fine granular soils (Table 1). More

detailed guides such as those published by the Air Force (Table 2) and by

Johnson (3) suggest stabilization methods for particular soil types based on

both their location in the pavement structure and the purpose or function of

their use (load carrying characteristics, waterproofing, etc.). Although

these guides do not quantitatively indicate soil types for particular

stabilizers, they do indicate the Importance of recognizing the purpose of

the use of the stabilizer in a particular location within the pavement

13

TABLE 1

MOST EFFECTIVE STABILIZATION METHODS

FOR USE WITH DIFFERENT SOIL TYPES

f Soil Type Most Effective Stabilization Methods

1. Coarse granular soils Mechanical blending, soil-asphalt, soil-cemen t, 1 ime-flyash

2. Fine granular soils Mechanical blending, portland cement stabilization, llne-flyash, soil- asphalt, chlorides

3. Clays of low plasticity Compaction, portland cement stabilization, chemical waterproofers, lime modification

4. Clays of high plasticity Lime stabilization |

[after U. S. Air Force (2)]

14

■ !

TABLE 2

SOIL TYPES AND STABILIZATION METHODS

WHICH APPEAR BEST SUITED FOR SPECIFIC APPLICATIONS

Purpose Soll Typ*. Recommended

Stabilization Mctt-oJs

1. Suhgrade Stabilization

Coarse granular SA. SC, MB, C A. Improved load carrying and stress distributing characteristics

Fine granular SA, SC, MB, C Clays of low PI C, SC. CMS, LMS, SL Clays of high PI SL, LMS

B. Reduce Frost susceptibility

Fine granular CMS. SA. SC, LF Clays of low PI CMS, SC, SL, CW, LMS

C. Waterproofing and Improved runoff

Clays of low PI CMS, SA, CW, LMS, SL

D, Control of shrinkage and swell

Clays of low PI CMS, SC. CW. C. LMS, SL Clays of high PI SL

E. Reduce resiliency Clays of high PI SL, LMS Elastic silts and clays SC, CMS

•• Base Course Stabilization

Fine granular SC, SA, LF, MB A. Improvement of substandard materials Clays of low PI SC^SL

B. Improved load carrying and stress distributing characteristics

Coarse granular SA, SC, MB, LF Fine granular SC, SA, LF, MB

C. Reduction of pumping Fine granular SC, SA, LF, MB, membranes

3. Shoulders (unsurfaced)

All soils See Section 1A above, Also MB

A. Improved load carrying ability

B. Improved durability All soils See section 1A above C. Waterproofing and

improved runoff Plastic soils CMS, SL, CW, LMS D. Control of shrinkage

and swell Plastic soils See section IE above

4. Dust Palliative Fine granular CMS, CL, SA, oil or bituminous surface spray

Plastic soils CL, CMS, SL, LMf

5. Ditch Lining Fine granular PSC, CS, SA Plastic soils PSC, CS

6. Patching and Reconstruction Granular soils SC, SA, LF, MB

KEY:

C Compaction CMS Cement Modified Soil CL Chlorides CS Chemical Solidiflers

CW Chemical Waterproofers PSC Plastic Soil Cement LF Lime Flyash SA Soil Asphalt

LMS Lime Modified Soil SC Soil Cement MB Mechanical Blending SL Soil Lime


15

structure.

Since general guides to soil stabilization have indicated that both the

purpose and the location in the pavement structure are important criteria

for a soil stabilization index system, and since the Air Force desires an

index system for both expedient and nonexpedient facilities, several

appropriate systems will be developed. The first system will be developed

to satisfy the Air Force requirement for expedient construction while the

second, the nonexpedient system, will be developed for use where laboratory

equipment and sufficient time are available for a more detailed analysis of

the soil-stabilizer mixture. The major subsystems of the soil stabilization

system as described previously are shown in Figure 1. As noted in this

figure, a further separation of subgrade and base course has been included

for both the expedient and nonexpedient soil stabilization systems.

2. Existing Guides for Selecting Stabilizing Agents

A gradation triangle, Figure 2, is being utilized by the Army and Air

Force (4) to assist the engineer in the proper selection of stabilizers.

This method makes use of the following soil index properties to determine the

proper type of stabilizer:

a. percent material retained on No. 4 sieve

b. percent material passing No. 200 sieve

c. percent material passing No. 4 sieve and retained on No. 200 sieve

d. Atterberg limits

As noted, the gradation triangle allows soils to be separated into

selected areas. The Unified Soil Classification System is then used to

further classify the soil, and appropriate Atterberg limit and gradation

restrictions are applied for the particular stabilizers.

16

. ,v iMWOSt ■■;,• - ;m<v»,>M

8 -d <o

- - PH ja

H M O <

M N

M H U W

w t/1

M <

W ►J c

M

H

H

CN

0) o o

Crt

: i

S 0)

M (0

002 ON NO Q3NIV13ä ONV 3A3IS V ON ONISSVd IVIbliVW) ONVC 1H9I3M AQ i.N33 U3d

17

Oglesby and Hewes (5) have presented a method of determining stabilizer

types which was modified after the original work of the Division of Physical

Research, Bureau of Public Roads (Figure 3). This method utilizes the

plasticity index (P.I.) and percent passing the No. 200 sieve together with

the American Association of State Highway Officials (AASHO) Soil Classifi-

cation System for the purpose of stabilizer selection.

3. Criteria for Lime Stabilization

Experience has shown that lime will react with all medium, moderately

fine, and fine grained soils to decrease plasticity, increase workability,

reduce swell, and Increase strength (6). Generally speaking, those soils

classified by AASHO as A-4, A-5, A-6, A-7 and some of the A-2-7 and A-2-6

soils are most readily susceptible to stabilization with lime. Soils

classified according to the Unified System as CH, CL, MH, ML, SC, SM, GC,

GM, SW-SC, SP-SC, SM-SC, GW-GC, GP-GC and GM-GC should be considered as

potentially capable of being stabilized with lime. Conversion from these

classifications to other soil classifications and strength indicators can be

accomplished by the use of Figure 4 (7) .

Robnett and Thompson (6), based on experience gained with Illinois soils,

have indicated that lime may be an effective stabilizer with clay contents

(<2y) as low as 7 percent, and furthermore soils with a P.I. as low as 8 can

be satisfactorily stabilized with lime (8) . Air Force criteria presented in

Figure 2 indicate that the P.I. should be greater than 12, while represent-

atives of the National Lime Association (NLA) (9) indicate that a P.I. greater

than 10 would be a reasonable criteria to utilize. Presumably, these

experiences reflect the fact that lower plasticity soils have insufficient

reactive components to produce worthwhile benefits.

18

■ K ■>"■■ ■■ ■*■**:.-■

30 -i 1 1 r Type and amount of admixture should

be determined by laboratory tests rTlTx x x x * x x * x x -* * * x X X X

\ Hydraded lime (Ca(OH)2l

^PnrtlanH rpmont

ä :*. *

-Portland cement ^ X V

A-2-AA-J A-2-6'

-Portland cement y'i'oniana cs

J yl-l-o I A-\-b

Not expected to need stabilizing admixture x; / cem<" ^^, | (AASHO M147-57) ^ ^x ^; ',

r^-3^.1 H-Bltumen^i'' ( Bitumen (> Bilumen, Portland cement, p^ /»r'l^^^J ( lAHCX I 1

or «ilty cli» will fC Vf*1-' "^Hs ,', ^ )'

>l-2-5 A-2-4

Portland,^

-4-6

A-4

X X X X X X V

10 15 20 25 30 35 Percentage of existing soil passing No. 200 sieve

40 45

FIGURE 3. Suggested stabilizing admixtures suitable for use with soils, as Indicated by plasticity Index and amount passing No. 200 sieve. (Source: Div. of Physical Research, Bureau of Public Roads, slightly modified).

[after Oglesby & Hewes (5)]

19

California Bearing Ratio—CBR <" S 6 7 8 9 10 15 20 25 30 40 SO 60 70 80 90100

BOO

(I) For the boiic idea, ice O J. Porter, "Founduiiom for Flaiible Pavementt," Highway Research Board Prcieedimji of the Jwenty tecond Annual Meeting. 1942, Vol. 22, pagei 100-1 36.

(3) "Characterjilic» of Soil Groupi Pertaining to Roods and Airfields," Appendix B, The Unified Soil Clattificalion Syilem, U.S. Army Corps of Engineers, Technical Memorandum 3-357, 1953.

(3) "Classification of Highway Subyrade Materials," Highway Research Board Proceedings of fhe Twwlf'fiflh Annual Meefing, 1945, Vot. 25, pages 376-393.

(4) Airpor* Paving, U.S. Department of Commerce, Federal Aviation Agency, May 1948, page» 11-16. Eiti* moled using values given in FAA Oetign Manual for Airport Povementi.

(5) F. N Hveem, "A New Approach for Pavement Design," Engineering Newi-Record, Vol. 141, No. 2, July 6, 1948, pages I 34 I 39. ft is factor used in California Stabilometer Method uf Design.

(6) See T. A. Middlebrooks and G E. Bertram, 'Soil Tests for Design of Runway Pavements," Highway Research Board Procit-dingi of the Twenty stcond Annual Meeting, 1 942, Vol. 22, page I 53. k is factor used in Westergaard's analysis for design of concrete pavement.

FIGURE 4. Approximate interrelationships of soil classifications and bearing values.

fafter Portland Cement Association (7)1

20

■''-" ■ '^mtm&ßSPimkm ' ■

4. Criteria for Cement Stabilization

The Portland Cement Association (PCA) (10, 11) indicates that all types

of soils can be stabilized with cement*. However, well-graded granular

materials that possess a floating aggregate matrix (an aggregate system with

the voids in the + No. 200 material overfilled with fines) have given the

best results. Suggested gradings to meet this floating aggregate matrix

concept should fall within the band specified in Table 3 (12).

Limits on the plasticity index have been established by the Air Force as

shown In Figure 2 and summarized in Table 4 for different types of soils. As

noted, the P.I. should be less than 30 for the sandy and gravelly materials

while the P.l. should be less than 20 for the fine grained soils. This

limitation is necessary to insure proper mixing of the stabilizer. A minimum

of 45 percent by weight passing the No. 4 sieve has been indicated as an

additional requirement for coarse granular materials.

Information developed by the Bureau of Public Roads (Figure 3) (5)

indicates that cement should be used as a stabilizer for materials with

less than 35 percent passing the No. 200 sieve and with a P.I. less than 20.

Thus this system implies that AASHO classified A-2 and A-3 soils can be best

stabilized by cement while A-4, A-5, A-6 and A-7 soils can be best stabilized

by lime.

5. Criteria for Bituminous Stabilization

The majority of bituminous soil stabilization has been performed with

asphalt cement, cutback asphalt and asphalt emulsion. Current design and

construction trends, particularly in the state highway departments, have

*Cement will be used herein to imply portland cement.

21

TABLE 3

GRADING LIMITS FOR CEMENT STABILIZATION

OF WELL GRADED GRANULAR MATERIALS

Sieve Size Limits 1

Passing No. 4 > 55 percent 1

1 Passing No. 10 > 35 percent

Passing No. 10, retained No. 200

> 25 percent i

[after Portland Cement Association (12)]

TABLE 4

ATTERBERG LIMIT REQUIREMENTS FOR CEMENT STABILIZED SOILS

Soil Classification (Unified Soil Clas-

| sification System)

Atterberg Limit j Requirement

SP-SM, SW-SM, SW-SC, SP-SC GW-GM, GP-GM, GW-GC GP-GC

P.I. < 30 j

| SM, SC, SM-SC GM, GC, GM-GC

p j. ,, „Q . (50 - fines content) * ' "* 4 |

1 CH, CL MH, ML OH, OL ML-CL

L.L. < 40 | P.I. < 20 |


22

.

indicated that stabilization of base courses with asphalt cements Is by far

the most popular form of bituminous stabilization (13). In general, those

materials which are most effectively stabilized with asphalt cement have

lower percentages of fines than those materials which have been stabilized

with cutback asphalt and emulsion.

Some of the earliest criteria for bituminous stabilization were developed

by the Highway Research Board Committee on Soil-Bituminous Roads. These

criteria were revised and published by Winterkorn (1A) and appear in Table 5.

The American Road Builders Association (15) made similar recommendations and

these are stuwu in Table 6.

The Asphalt Institute (16) grading and plasticity requirements for

bituminous base course specifications require:

a. less than 25 percent passing the No. 200 sieve

b. sand equivalent not less than 25

c. plasticity index less than 6

Herrin has presented (17) and revised (18) a table (Table 7) recommending

suitable soils for stabilization by bituminous materials. Contained in this

table are recommendations on the suitability of various soils with certain

percentages of minus No. 200 material, and certain liquid limit and plasticity

index ranges.

Certain limits have been developed by the Asphalt Institute's Pacific

Coast Division, Chevron Asphalt Company and Douglas Oil Company for emulsion

treated materials. The requirements recommended by the Asphalt Institute (19)

(Table 8) suggest that the percent of minus No. 200 material should be in a

range of 3-15 percent, the plasticity index should be less than 6, and the

product of the plasticity index and the percent passing the No. 200 sieve

should not exceed 60. The Chevron Asphalt Company (20) has presented

23

TABLE 5

TYPES OF SOIL BITUMEN AND CHARACTERISTICS OF SOILS

EMPIRICALLY FOUND SUITABLE FOR THEIR MANUFACTURE

Sieve Analysis

Soil Bitumen, t

%

Sand Bitumen,

%

Waterproofed Granular Stabilization, %

Passing: A B C

1 1/2-ln. 100

1-in. t 80-100 100

3/4-in. , . . 65-85 80-100 100

No. 4 >50 100 40-65 50-75 80- -100

No. 10 . .. 25-50 40-60 60- -80

No. 40 35-100 15-30 20-35 30- -50

No. 100 10-20 13-23 20- -35

No. 200 10-50 <12; <25 § 11 8-12 10-16 13- -30

Characteristics of Fraction P issing No. 40 Sieve

Liquid limit <40

Plasticity index <18 <10; <15 <10; <15 <10; <15 1i

Field moisture equlv. <20 § • • • • • • . .

Linear shrinkage ^5 § • • ■ • • ■ • •

t Proper or general.

+ Maximum size not larger than 1/3 of layer thickness; if compacted in several layers, not larger than thickness of one layer.

§ Lower values for wide and higher values for narrow gradation band of sand. If more than 12% passes, restrictions are placed as indicated on field moisture equivalent and linear shrinkage.

| | A certain percentage of -200 or filler material is indirectly required to pass supplementary stability test.

H Values between 10 and 15 permitted in certain cases.

[after Winterkorn (14)]

24

TABLE 6

GRADING AND PLASTICITY REQUIREMENTS

FOR SOIL-BITUMEN MIXTURES

Sieve Size

No. 40

No. 200

Percent Passing

50 - 100

0-35

Atterber« Limits

Liquid limit

Plasticity index

Maximum Value

30

10

[after American Road Builders Association (15)]

25

TABLE 7

ENGINEERING PROPERTIES OF MATERIALS

SUITABLE FOR BITUMINOUS STABILIZATION

% Passing Sieve

Sand-Bitumen Soil-Bitumen Sand-Gravel-Bitumen

1-1/2" 100

1" 100

3/4" 60-100

No. 4 50-100 50-100 35-100

10 40-100

40 35-100 13-50

100 8-35

200 5-12 good - 3-20 fair - 0-3 and 20-30 0-12 poor - > 30

Liquid Limit good - < 20 fair - 20-30 poor - 30-40 unusable - > 40

Plasticity Index < 10 good - 5 fair - 5-9 poor - 9-15 <10 unusable - > 12-15

Includes slight modifications later made by Herrin.

[after Herrin (17)]

26

TABLE 8

GRADING, PLASTICITY AND ABRASION REQUIREMENTS FOR

SOILS SUITABLE FOR EMULSIFIED ASPHALT TREATED BASE COURSE

Sieve Size

Percent Passing by Weight

2 inch maximum 1-1/2 inch 3/4 inch maximum maximum

2-1/2 inch 100

2 inch 90-100 100

1-1/2 inch 90-100

1 inch 100

3/A inch 50-80 50-80 80-100

No. 4 25-50 25-50 25-50

No. 200 3-15 3-15 3-15

Other Requirements

6 maximum 75 minimum

a. Plasticity Index b. resistance Value c. Loss in Los Angeles

Abrasion Machine 50 percent maximum d. Product of Plasticity Index and the

percent passing the No. 200 sieve shall not exceed 60.

[after The Asphalt Institute, Pacific Division (19)]

27

criteria (Table 9) which Indicate that the California sand equivalent test

should be used as a measure of the plasticity requirements for the soil

and should have a minimum value of 30. Up to 25 percent passing the

No. 200 sieve Is allowed for the material Identified as sllty sand.

Dunning and Turner (21) of the Douglas Oil Company have presented

guidelines for emulsion stabilization as shown In Table 10.

Materials Research and Development, Inc. of Oakland, California, has

recently published a guide for asphalt stabilization for the U. S. Navy (22)

in which criteria recommended by the Asphalt Institute and Chevron Asphalt

Company have been utilized. This guide recommends that the maximum amount

passing the No. 200 sieve should be less than 25 percent, the plasticity

index less than 6, sand equivalent more than 30, and the product of the

plasticity index and the percent passing the No. 200 sieve less than 72 In

all cases. These criteria apply when both cutback asphalt and emulsified

asphalt are used as soil stabilizers. The griding requirements (Table 11)

for sands and semi-processed materials are identical to those recommended

in Table 9 by Chevron Asphalt Company.

Grading requirements for materials to be stabilized with asphalt cement

in a central plant have not been adequately defined. In general, those

materials that are specified as suitable for asphalt concrete surface courses

are more than adequate for base courses. Most asphalt treated base course

specifications, however, will allow a larger maximum size of aggregate and

the grading band is not as restrictive. A recent review of state highway

specifications gives detailed information on these grading bands (13). For

example, Texas (23) and California (24) have grading specifications as shown

in Table 12. In addition, Texas specifies a maximum liquid limit of 35 and

a maximum plasticity index of 6. The majority of the state highway depart-

28

Sem

i-P

roce

ssed

C

rush

er, P

it or

Bank

Run

A

ggre

gate

s

100

80-1

00

25-8

5

3-15

30 M

in.

60 M

in.

60 M

ax.

(0 Q z < (0

100

75-1

00

15-6

5 12

-25

30 M

in.

60 M

in.

100

75-1

00

35-7

5 15

-30

5-12

30 M

in.

NP

60 M

in.

-1

100

75-1

00

0-12

30 M

in.

NP

60 M

in.

Pro

cess

ed

1

Den

se

Gra

ded

A

ggre

gate

s

100

90-1

00

65-9

0

30-6

0 15

-30

7-25

5-

18

4-12

30 M

in.

78 M

in.

50 M

ax.

AS

TM

T

est

M

eth

od

C-1

36

D-2

419

D-4

24

C-1

31

o O) 4) 15 Ü G

rad

atio

n:

1^2"

% P

assi

ng

1

"

V2"

#

4 16

50

100

200

San

d E

qu

ival

ent, %

Pla

stic

ity

Ind

ex

Un

trea

ted R

esis

tan

ce

R V

alu

e

Loss

in

Los

An

gel

es

Rat

tler

(a

fter

500

rev

olu

tio

ns)

o ^ «D <N C K ^^ 3 T-

o •- • o

3 ™ w iH O m CS

K 43 ^ 7 a S" J8 8* n r- § 0) < H - »- > «rf 0)

0) X 6 > (0 |5 0)

4J

3 $ (d 5 W '—'

29

■

TABLE 10

GUIDELINES FOR EMULSIFIED ASPHALT STABILIZATION

! Test Requirements

Good Fair Poor

% passing No. 200 sieve 3-20 0 - 3, 20 - 30 >30

Sand Equivalent >25 15 - 25 <15 |

Plasticity Index < 5 5 - 7 > 7

[after Dunning and Turner (21)]

TABLE 11

GRADING REQUIREMENTS FOR SANDY AND SEMI-PROCESSED MATERIALS

Sieve

Size

Percent passing sieve for soils that are:

Poorly-graded sands

Well-graded sands

Silty sands

Semi- processed*

1 1 1/2" — — — 100

1 1" — — — 80 - 100 1

1 3/4" — — — 1 1/2" 100 100 100 —

H 75 - 100 75 - 100 75 - 100 25-85

//16 — 35 - 75 — 1

1 #50 — 15 - 30 — i

| #100 — — 15 - 65 I #200 0-25 5-12 12 - 25 3-15

*Semi-processed crusher, pit, or bank-run aggregates.

[after U. S. Navy (22)]

30

TABLE 12

TYPICAL ASPHALT CEMENT TREATED BASE COURSE REQUIREMENT

Sieve Size Percent Passing by Weight \

California Texas

1 3/4 Inch 97-100

1 1/4 Inch 100

1 Inch 95-100

3/4 Inch 80-95

3/8 Inch 50-65

No. 4 35-50

No. 10 30-55

No. 30 12-25

No. 200 2-7

[after references 23 and 24]

31

■■ ■ ■ ■ ■• " ■ ,■ ■ ■

ments recommended 12 percent or less passing the No. 200 sieve.

Air Force recommendations for gradlngs of materials suitable for asphalt

cement treated base course are shown In Table 13 (25). Although gradations

6, 7, 8 and 9 are specifically recommended, It Is believed that all gradations

are practical, provided they are economically feasible.

Materials that are suitable for bituminous treatment Include AASHO

classified A-l-a, A-l-b, A-2-4, A-2-6, A-3, A-4 and low plasticity A-6

soils (26), and soils classified by the Unified Classification System as SW,

SP, SW-SM, SP-SM, SW-SC, SP-SC, SM, SC, SM-SC, GW, GP, GW-GM, GP-GM, GW-GC,

GP-GC, GM, GC and GM-GC provided certain plasticity and grading requirements

are met.

If the plasticity Index or the percent passing the No. 200 sieve exceeds

the values cited above, then experience shows that the Intimate mixing of the

bitumen and soil necessary for satisfactory stabilization is nearly Impossible.

6. Criteria for Combination Stabilization

Combination stabilization is herein defined specifically as lime-cement or

lime-bituminous combinations. The purpose of using combination stabilizers is

to reduce plasticity and increase workability with lime so that the soil may

be effectively stabilized with the secondary stabilizer.

Robnett and Thompson (26) have reviewed the literature and have sug-

gested that soils which may be treated by these combination stabilizers are

AASHO classified A-6 and A-7 soils and certain A-4 and A-5 soils (6)

The advantages of using lime in certain bituminous stabilization con-

struction operations have been alluded to in references 27, 28 and 29.

Most Importantly, the addition of lime may prevent the stripping of asphalts

from certain aggregates and thus make the mix more nearly waterproof.

32

>

TABLE 13

AGGREGATE GRADATION SPECIFICATION LIMITS FOR BITUMINOUS PAVEMENTS

1 ESS »MlSMtlOD

1 (Sqxar* 1 OMitlim)

Percentage by Weight (Paaaln«} l.l/S-ln. Vkximm 1-ln. MaxlaiB 3/4-ln. Max

ace Course

Ina 1/2-ln. Kaxlwa 3/«! in. Haxlmv» I

Sari

Gradation 1 Gradation 2 Gradation 1 Gradation 4 Gradation ? a \> e a b e a b e a b e a V c !

1 l-l/S-ln. 100 100 100 X-lo. 79-95 83-96 86-98 100 100 100 — ... — 3A-ln. .-• 80-95 8U-96 90-96 100 100 100 .-. ... .-- 1/8-in. 6il75 66179 71-84 68-86 7U-89 79-93 60-95 64-96 67-96 100 100 100 »mm --- i 3/e-in. • -* ... --. — ... ... 79-94 81-95 66.96 100 100 100 1 >o. k

31-^3 uilio SU-66 l»5-60 52-66 60-75 55-70 61-74 67-80 59.73 64-80 72-85 75-95 S:£ 80-95

Mo. 10 37-V9 U3-55 38-47 39-51» 47-62 40-54 46-60 54.66 43-57 50-64 57-''0 56-76 62-84 »o. UO 16-25 20-29 25-3k 16-26 21-32 26-37 22-31 26-35 31.40 23-33 27-37 31-42 26.44 29-47 32-50 •o. SO 10-17 12-19 15-22 10-18 13-21 15-24 12-20 15-23 19-26 13-20 16-23 19-26 14-26 16-30 18-32 Ho. 200* 3-6 3.5-6.5 4.7 3-7 3.5-7.5 4-6 3-7 3.5-7.5 4-6 l»-e 4-6 44 5-9 6-10 7-11

Gradation 6 . Gradation

Binder Courae

6 Gradation 9 7 . Gradation a fc e a b c _ a b c a b c _

1 1.1/2-In. 100 100 100 1 1-ln. 73-95 75-95 79-95 100 100 100 ...

3A-ln. 72-95 75-95 81-96 100 100 100 ..- ... .-. 1/2-ln. 55-73 59-77 eäläo 61-82 65-65 69-89 70-95 74-95 77.95 100 100 IK 3/8.1n. mmm .-. .*- ... 60-80 64-64 68-88 71-95 75.95 78-95 Ho. U 35-51 39-55 l»2-58 38-54 43-59 48-66 42-60 47-65 52-70 50-71 54-75 59.80 Ho. 10 23-38 27-U2 31-U6 25-41 29-45 34-50 28-46 33-51 36.54 32-53 36-57 41.62 Ho. UO 11-21 13-23 15-25 12-23 14-25 17-26 14-26 16-28 18-30 16-29 16.31 21-34 Ho. 60 6-11. 7-15 8-16 7-16 8-17 10-18 6-18 9-19 10-20 10-20 11-21 12.22 Ho. 200* 3-7 3-7 3-7 3-7 3-7 3-7 3-7 3-7 3-7 1..9 4-9 4-9

1-ln.

All Bixh-preMun Tire and Tar-rubber Surfaea Couraaa

Gradation 10 Gradation 11 a b e a b e

100 3A-ln. 84-97 — 100 —. 1/2-ln. 74-88 62-96 — 3/8-In. 68-62 75-90 ... Ho. U 54-67 — 60.73 — — Ho. 10 36-51 43-57 --. ... Ho. 20 26-39 29-43 Ho. UO 17-30 — 19-33 ... Ho. 80 9-19 10.20 ... — Ho. 200* 3-6 3-6 -— .—

[after U. S. Army (25)]

33

7. Summary of Criteria for Selecting Stabilizing Agents

Criteria have been presented which represent wide ranges of opinion as

to the types of soils that can be stabilized by certain stabilizers. Most

published Information gives reference to soils classified either by the AASHO

or Unified Soil Classification Systems; however, the authors feel that a more

appropriate separation of soils for stabilization can be made utilizing

Atterberg limits and gradation. It should be remembered that both Atterberg

limits and gradation are relatively easy to determine in the laboratory and

both are necessary inputs for the AASHO and Unified Soil Classification

Systems.

Criteria selected for utilization in this index system are based on the

recommendations cited previously and by personal conversation with representa-

tives of the University of Washington, Washington State University, University

of Idaho, University of California, Oregon Highway Department, United States

Forest Service, Chevron Asphalt Company, Asphalt Institute, Portland Cement

Association, National Lime Association and private consultants. It should be

recognized that unaminous agreement was not possible on the selection of

these criteria. The criteria sheeted are as follows:

I. Expedient construction

A. Subgrade

1. Lime stabilization

Minimum plasticity index of 10

2. Cement stabilization

Maximum plasticity index of 30

3. Bituminous stabilization

a. Maximum plasticity index of 10

34

b. Maximum of 25 percent passing No. 200 sieve

4. Lime-Cement stabilization

a. Minimum soil plasticity index of 10 b. Minimum of 25 percent passing No. 200 sieve c. Reduce plasticity index of soil to less than

30 with lime prior to the addition of cement

5. Lime-Bituminous stabilization


10 with lime prior to the addition of the bitumen

B. Base course






a. Maximum plasticity index of 6 b. Maximum of 25 percent passing No. 200 sieve c. Product of plasticity index and percent passing

No. 200 sieve less than or equal to 72





6 with lime prior to the addition of bitumen

II. Nonexpedient construction

A. Subgrade


35

Minimum plasticity of index of 10




a. Maximum plasticity Index of 10 b. Maximum of 25 percent passing No. 200 sieve


a. Minimum soil plasticity index of 10 b. Minimum of 25 percent passing No. 200 sieve c. Reduce plasticity Index of soil to less than




10 with lime prior to the addition of the bitumen

B. Base course






a. Maximum plasticity index of 6 b. Maximum of 25 percent passing No. 200 sieve c. Product of plasticity index and percent passing

No. 200 sieve less than or equal to 60





a. Minimum soil plasticity index of 10

36

es ■ .■■* •■-•

b. Minimum of 25 percent passing No. 200 sieve c. Reduce plasticity Index of soli to less than

6 with lime prior to the addition of bitumen

Adoption of the above criteria allows the development of Figures 5, 6, 7

and 8 which serve as the Intltlal breakdown of the soils Into groups with

which soil stabilizers can be associated. Because of the relative simplicity

of the tests Involved, the system can be used with minor alterations for

both expedient and nonexpedlent construction operations. As noted on

Figures 5 and 6, slightly different criteria are used for base and subgrade

stabilization for the reasons cited previously.

the engineer should be aware of certain environmental conditions and

construction limitations that restrict the use of the stabilizers. Listings

of these conditions in the form of precautions for lime, cement and bituminous

stabilization are given in Tables 14, 15 and 16, respectively.

37

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41

TABLE 14

ENVIRONMENTAL AND CONSTRUCTION PRECAUTIONS

FOR LIME STABILIZATION

Item Location of Stabilized Layer

I Expedient Subgrades A. Environmental - If the soil temperature is less than 40oF and Is not expected to Increase for one month, chemical reactions will not occur rapidly, and the strength gain of the lime-soil mixture will be minimal. If these environmental conditions are expected the lime may act as a soil modifier. B. No construction precautions necessary.

II Expedient Base Courses A. Environmental - If the soil temperature is less than 60 to 70oF and is not expected to increase for one month, chemical reactions will not occur rapidly, and the strength gain of the lime-soil mixture will be minimal. If these environmental conditions are expected an alternative stabilizer should be investigated for possible use. B. Construction - If heavy vehicles are allowed on the lime stabilized soils prior to a 10 to 14 dav curing period, certain pavement damage can be expected.

Ill Nonexpedient Subgrades A. Environmental - If the soil temperature is less than 60 to 70oF and is not expected to increase for one month, chemical reactions will not occur rapidly, and the strength gain of the lime-soil mixture will be minimal. If these environmental conditions are expected the line may act as a soil modifier. Lime-soil mixtures should be scheduled for construction such that sufficient durability will be gained to resist any freeze-thaw cycles expected. B. Construction - If heavy vehicles are allowed on the lime stabilized soils prior to a 10 to 14 dav curing period, certain pavement damage can be expected.

IV Nonexpedient: Base Courses A. Environmental - If the soil temperature is less than 60 to 70oF and is not expected to increase for one month, chemical reactions will not occur rapidly, and the strength gain of the lime-soil mixture will be minimal. If these environmental conditions are expected the lime may be expected to act as a soil modifier. Lime-soil mixtures should be scheduled for construction such that sufficient durabilitv will be gained to resist any freeze-thaw cycles expected. B. Construction - If heavy vehicles are allowed on the lime stabilized soils prior to a 10 to 14 dav curing period, certain pavement damage can be expected.

42

■ ■ a":.. ,.: ■}■:.■ ■■

TABLE 15


FOR CEMENT STABILIZATION

Item Location of Stabilized Layer

I Expedient Subgrades A. Environmental - If the soil temperature Is less than 40oF and Is not expected to Increase for one month, chemical reactions will not occur rapidly, and strength gain of the cement-soil mixture will be minimal. If these environmental conditions are expected the cement may act as a soil modifier. B. Construction - If heavy vehicles are allowed on the cement stabilized soils prior to a 10 to 14 day curing period, certain pavement damape can be expected. Construction during periods of heavy rainfall should be avoided. Compaction of cement stabilized soil should be completed within 5 to 6 hours after spreading and mixing.

II Expedient Base Courses A. Environmental - If the soil temperature is less than 60 to 700F and is not expected to increase for one month, chemical reactions will not occur rapidly, and strength gain of the cement-soil mixture will be minimal. If these environmental conditions are expected, an alternative stabilizer should be investigated for possible use. B. Construction - If heavy vehicles are allowed on the cement stabilized soils prior to a 10 to 14 diy curing period, certain pavement damage can be expected.

Ill Nonexpedient Subgrades A. Environmental - If the soil temperature is less than 60 to 70oF and Is not expected to increase for one month, chemical reactions will not occur rapidly, and strength gain of the cement-soil mixture will be minimal. If these environmental conditions are expected the cement may act as a soil modifier. Cement-soil mixtures should be scheduled for construction such that sufficient durability will be gained to resist any freeze-thaw cycles expected. B. Construction - If heavy vehicles are allowed on the cement stabilized soils prior to a 10 to 14 day curing period, certain pavement damage can be expected.

IV Nonexpedient Base Course^ A. Environmental - If the soil temperature is less than 60 to 70oF and is not expected to increase for one month, chemical reactions will not occur rapidly, and strength gain of the cement-soil mixture will be minimal. If these environmental conditions are expected the cement may be expected to act as a soil modifier. Cement-soil mixtures should be scheduled for construction such that sufficient durability will be gained to resist any freeze-thaw cycles expected.

B. Construction - If heavy vehicles are allowed on the cement stabilized soils prior to a 10 to 14 day curing period, certain pavement damage can be expected.

43

TABLE 16


FOR BITUMINOUS STABILIZATION

Condition Precautions

Environmental When asphalt cements are used for bituminous stabilization» proper compaction must be obtained. If thin lifts of asphalt concrete are being placed, the air temperature should be 40oF and rising, and compaction equipment should be used Immediately after lay down operation. Adequate compaction can be obtained at freezing temperatures If thick lifts are utilized. When cutbacks and emulsions are utilized, the air temperature and soil temperature should be above freezing. Bituminous materials should completely coat the soil particles before rainfall stops construction.

Construction Central batch plants, together with other specialized equipment, are necessary for bituminous stabilization with asphalt cements. Hot dry weather is preferred for all types of bituminous stabilization.

(Note: These requirements are applicable to base courses and subgrades for both expedient and nonexpedient operations.)

44

.*!**mw^-*<jw*iavim&w>mp^ *<rr**K-"-s ■

SECTION IV

DESIGN SUBSYSTEM FOR BITUMINOUS STABILIZATION

1. Introduction

The majority of bituminous stabilization construction is performed with

asphalt cements, cutback asphalts, and emulsified asphalts. Road tars have

been used, but it is felt that sufficient quantities have not been utilized

to warrant their inclusion in this index system. Soils which lend themselves

to stabilization with the above mentioned bituminous materials have been

defined in Section III of this report. In order to complete a design sub-

system for bituminous stabilization, criteria must be included to allow for

the following:

a. selection of the type of bitumen

b. selection of the quantity of bitumen

c. method of evaluating the bitumen-soil mixture

This section of the report will summarize criteria recommended by

various agencies and will select what is believed to be the best criteria

for use in the bituminous stabilization subsystem.

2. Selection of the Type of Bitumen

An indication of the type of bitumen to use for certain types of soils

has been suggested by the Asphalt Institute (16) , Herrin (17) , the Navy (22) >

the Air Force (30) and Chevron Asphalt Company (20). The Asphalt Institute(16)

suggestions are shown in Table 17 while the recommendations of Herrin (17),

45

TABLE 17

SUITABLE TYPES OF BITUMEN FOR STABILIZATION

| Type of Soils Cutback Asphalts Emulsions

Open-graded aggregate RC-250, RC-800 MS-2 j

Well-graded aggregate with little or no fine RC-250, RC-800 MS-2 aggregate and material MC-250, MC-800 SM-K passing the No. 200 SC-250, SC-800 SS-1, SS-K | sieve

Aggregate containing a considerable per- SS-1, SS-lh j centage of fine agg- MC-250, MC-800 SS-K, SS-Kh i

1 regate and material SC-250, SC-800 MS-2 passing the No. 200 CM-K sieve

[after the Asphalt Institute (16)]

46

■ -v ' - ••:•■: ■ •

which are similar, are shown In Table 18.

The Navy's (22) method to select emulsions and cutback asphalts Is

shown in Table 19 and Figure 9, respectively. The selection of the particular

type of emulsion is based on the percent of the soil passing the No. 200 sieve

and the relative water content of the soil, while the selection of the partic-

ular type of cutback asphalt is based on the percent passing the No. 200 sieve

and the ambient temperature of the soil. The basis of selection between these

two general kinds of asphalt depends on which kind is more readily available

for a particular Job. Air Force (30) recommendations are very general in

nature and indicate the MC-70, MC-250, MC-800, RC-70, RC-250, RC-800 cutbacks

and SS-1 emulsions are normally used. Soils which possess some fines or

natural binders and are well graded can be stabilized with medium curing

cutbacks; however, the rapid curing cutbacks are preferred.

Chevron Asphalt Company (20) recommends emulsions that conform to the

specifications shown in Table 20. The selection of either a cationic or

anlonic emulsion should be based on the type of aggregate that is used.

Mertens and Wright (31) have developed a method by which an aggregate can be

classified (Figure 10) to Indicate its probable surface charge and to determine

the type of emulsion (anionic or cationic) that is more suitable for the

particular type of aggregate (Figure 11). In general, Chevron recommends SS

and CM type emulsions with damp or wet aggregate mixes.

The use of asphalt cement stabilization is widespread In the highway

departments in the United States. Seventy-one percent of all bituminous

bound base courses placed by the state highway agencies in 1968 were made with

asphalt cement and mixed in a hot plant (13) . In addition, several cities and

counties are using this type of stabilization. It is therefore important that

its advantages be fully explored by the Air Force.

47

TABLE 18

SUITABLE TYPES OF BITUMINOUS MATERIALS

i

Crushed Stones

and

j Sand-Bitumen Soil-Bitumen S and-Grave 1-B1 tumen

Hot Mix: Cold Mix: Hot Mix:

! (a) (a) | AC- 85-100 RC-70,250,800 AC- 85-100 j | 120-150

(a) (b) MC-70,250,800 120-150

! (b) (b) ! 85-100 85-100 | 100-120 SC-70,250,800 100-120 ! 120-150 120-150

Cold Mix: Cold Mix:

(a) (b) RC-70,250,800 (a) (b) RC-70,250,800 1 MC-250,800 MC-250,800

i Emulsions Emulsions Emulsions 1

1 (a) (b) (a) (b) (a) (b)

! SS"1 SS-1 SS-1 MS-2

I (a) (a) | SS-lh SS-lh (a) | SS-K SS-K CM-K i SS-Kh SS-Kh 1 SM-K SM-K 1 (a) Refers to Asphalt Institute Nomenclature.

(b) Refers to Illinois Division of Highways Nomenclature.

[after Herrin (17)]

48

.■•■•■■-.■

TABLE 19

SELECTION OF TYPE OF EMULSIFIED ASPHALT FOR STABILIZATION

Percent Passing

// 200 Sieve

Relative Water Content of Soil

Wet (5%+) Dry (0-5%)

0-5 SS-lh (or SS-Kh) SM-K (or SS-lh*)

5-15 SS-1, SS-lh (or SS-K, SS-Kh) SM-K (or SS-lh*. SS- -1*)

15-25 SS-1 (or SS-K) SM-K

*Soll should be pre-wetted with water before using these types of emulsified asphalts.


49

'Iff 7/

\i '

Temperature of Aggregate."F

140 RC

Type of Cutback

MC

115

100

90

65

40

Grade of Cutback

SO Old New 5 3000

4 1500

3 800

250

70 0 1012.5 25

Percent Passing No. 200 Sieve

Example: For aggregate temperature of 100oF and 10% passing //200 sieve,use MC 800 cutback.

FIGURE 9. Selection of type of cutback for stabilization


50

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SILICA CONTENT

APPROXIMATE EFFECTIVE RANGE OF

CATIONIC EMULSION

\ APPROXIMATE \ EFFECTIVE RANGEN

OFANIONIC EMULSIONS

I000/o

100% ALKALINE OR ALKALINE EARTH OXIDE CONTENT

FIGURE 11. Approximate effective range of cationic and anlonlc emulsions on various types of aggregates

[after Mertens and Wright (31)]

53

Federal specifications for aaphalt cements, cutback asphalta and

emulsified asphalts are given In Tables 21, 22 and 23 respectively. These

specifications closely parallel those recommended by the Asphalt Institute (16).

3. Selection of the Quantity of Bitumen

Methods which have been used for the determination of asphalt content

for stabilized materials can be conveniently separated Into methods based on

laboratory tests performed on the soil, methods based on laboratory tests

performed on the soil-asphalt mixture and those based on a combination of

these two. A discussion of these methods follows.

a. Methods based on laboratory tests performed on the soil

These approaches are based on the quantity of asphalt necessary to

coat the surface of the soil particles. A general equation for computing

the quantity of asphalt Is:

A = SA x t x Y 'a

where:

A ■ percent asphalt

t = asphalt film thickness

SA = surface area of soil or aggregate

Y • unit weight of asphalt

This equation has been quantified empirically by the Asphalt Institute (16),

Oklahoma Department of Highways (32), McKesson (33) and Bird (34).

The Oklahoma Equation (32) developed for cutback asphalts has the

following form:

p - k + 0.005 (a) + 0.01 (b) + 0.06 (c)

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TABLE 23

SPECIFICATIONS FOR EMULSIONS

AN10NIC

Rapid Setting Medium Setting Slow Si ätting Tests RS-1 RS-2 MS-1 MS-2 SS-1 SS-lh

TESTS ON EMULSION

Viscosity, Furol, 60 ml., 77*Ff sec. 20-100 — — 100-700 20-100 20-100 Viscosity, Furol, 60 ml., 122>F., sec. — 75-400 50-500 — — — Residue by distillation, percent 57-62 62-69 60-67 62-69 57-62 57-62 Settlement, 7 day, maximum, difference 3 3 3 3 3 3 Demulslblllty:

50 ml. 0.10 N CaCl2> percent — — — 0-30 — — 35 ml. 0.02 N CaCl2, percent 60+ 60f — — ~ —

Sieve test, maximum, percent 0.10 0.10 0.10 0.10 0.10 0.10 Misclblllty with water, hours — — — 2 — — Aggregate Coatlng-Uater Resistance test — ~ Pass — ~ — Cement mixing test, maximum percent — — — — 2.0 2.0 Oil Distillate, percent by volume, max. — — 12 — — —

TESTS ON RESIDUE FROM DISTILLATION TEST

Penetration, 77'?., 100 gm., 5 sec. 100-200 100-200 100-200 100-200 100-200 40-90 Soluble in CCl^, minimum percent 97 97 97 97 97 97 Ash, maximum, percent 2 2 2 2 2 2 Ductility at 77*F, minimum, cm. 40 40 40 40 40 40

CATI0NIC

Rapid Setting Medium Setting Slow Setting Tests RS-2K RS-3K SM-K CM-K SS-K SS-Kh

TESTS ON EMULSION

Viscosity, Furol, 60 ml., 770F, sec. — — — — 20-100 20-100 Viscosity, Furol. 60 ml., 122'F, sec. 20-100 100-400 50-500 50-500 ~ — Residue by distillation, percent 60-65 65-72 60-65 65-72 57-62 57-62 Settlement, 7 day, max., difference 3 3 3 3 3 3 Sieve test, maximum, percent 0.10 0.10 0.10 0.10 0.10 0.10 Aggregate Coating-Hater Resistance test

Dry Aggregate (Job), min. pet. coated — — 80 80 — — Wet Aggregate (Job), min. pet. coated —> — 60 60 — ~

Cement mixing test, maximum percent — ~ ~ — 2 2 Particle Charge test Positive Posltlve Positlve Positive ~ — pH, maximum — ~ — — 6.5 6.5 Oil Distillate , percent by volume, max. 5 5 20 12 — —

TESTS ON RESIDUE FROM DISTILLATION TEST

Penetration, 77,F., 100 gm., 5 sec. 100-250 100-250 100-250 100-250 100-200 40-90 Soluble in CCI4. minimum, percent Ductility at 77^., minimum, cm.

98 98 98 98 97 97 40 40 40 40 40 40

[taken from Federal Specification SS-A-00674C]

57

where:

p ■ percent of residual asphalt by weight of dry aggregate

a - percent mineral aggregate passing the No. 10 sieve

b ■ percent mineral aggregate passing the No. 40 sieve

c ■ percent mineral aggregate passing the No. 200 sieve

k « 1.5 If plasticity Index < 8 and 2.0 If plasticity index > 8

The Asphalt Institute (.16) adopted a method for use with cutbacks

and emulsions as follows:

1. Cutbacks

p = 0.02 (a) + 0.07 (b) + 0.15 (c) + 0.20 (d)

where:

p = percent of residual asphalt by weight of dry aggregate

a = percent of mineral aggregate retained on No. 50 sieve

b - percent of mineral aggregate passing No. 50 sieve and

retained on No. 100 sieve

c = percent of mineral aggregate passing No. 100 sieve and

retained on No. 200 sieve

d - percent of mineral aggregate passing No. 200 sieve

2. Emulsions

p - 0.05 (a) + 0.1 (b) + 0.5 (c)

where:

p = percent by weight of asphalt emulsion, based on dry weight

of mineral aggregate


b ■ percent of mineral aggregate passing No. 8 sieve and

retained on the No. 200 sieve

c ■ percent of mineral aggregate passing the No. 200 sieve

58

This equation has also been utilized by the Navy (22) for cutback

stabilization.

McKesson's (35) formula, given below, is similar in form to the

Asphalt Institute's formula:

P = 0.75 (0.05A + 0.010B + 0.50C)

where:

P - percent of asphalt emulsion by weight of dry sand

A » sand retained on the No. 10 sieve in percent

B ■» sand passing the No. 10 sieve and retained on the No. 200

sieve In percent

C ■ sand passing the No. 200 sieve in percent

Bird (34) has presented two formulas to use depending on the percent

passing the No. 200 sieve.

Formula (1) T = 0.02F + 0.1C + A

(for use with sands having a minimum of 50 percent passing the No. 10

sieve and 5 to 12 percent passing the No. 200 sieve)

Formula (2) T - 0.2F + 0.1D + 4

(for use with sands having a minimum of 50 percent passing the No. 10

sieve and more than 12 percent passing the No. 200 sieve)

where:

T ■ pounds of emulsified asphalt per cubic foot of loose,

dry aggregate

F = percent aggregate passing the No. 10 sieve

C ■ percent aggregate passing the No. 200 sieve

D - difference, plus or minus, between 24 and C above

The California Centrifuge Kerosene Equivalent (CKE) Method is based

on surface area as well as particle surface characteristics. The com-

59

plete California CKE Method can be found In California Test Method 303

(35); however, a revised method has been suggested for use by the Navy

(22). The CKE method is suitable for asphalt cement, cutback, and

emulsified asphalt stabilized materials.

The Navy (22) has also suggested emulsion quantities to be used for

certain soils based on the percent passing the No. 10 sieve and percent

passing the No. 200 sieve (Table 24). The development of the table was

based on surface area and void content theory,

b. Methods based on laboratory tests performed on the soil-asphalt mixture

Several laboratory test methods have been used to assist the engineer

in determining the asphalt content of stabilized mixtures. For con-

venience these can be separated into:

1. Methods for use with hot-mix asphalt cement stabilized materials

2. Methods for use with liquid asphalts (cutbacks and emulsions).

A recer t Highway Research Board Commietee Report (13) has summarized

design methods and criteria used for coarse aggregate type hot plant

mixed bases. As shown on Table 25 the Hveem and Marshall methods of

design are in popular use, but the criteria vary from state to state.

Several states Indicated the use of Marshall stability and unconfined

compresslve strength; however, they did not indicate criteria. Three

states (Oregon, Washington and Wyoming) indicated the use of modified

Immersion-compression tests.

Marshall method criteria utilized by the Air Force (2) are shown in

Table 26. The criteria listed for asphaltic concrete binder course are

suitable for use with coarse graded aggregate hot-mix base courses while

the criteria for sand-asphalt should be used for these particular types of

asphalt cement treated materials. The Air Force has indicated that the

60

W«W)SWR».»f*ri

TABLE 24

EMULSIFIED ASPHALT REQUIREMENT

Percent passing No. 200

Lbs. of emulsified asphalt per 100 lbs. of when percent passing No. 10 sieve

dry aggregate Is:

50* 60 70 80 | 90 j 100

0 6.0 6.3 6.5 6.7 7.0 7.2

2 6.3 6.5 6.7 7.0 7.2 7.5

4 6.5 6.7 7.0 7.2 7.5 7.7

6 6.7 7.0 7.2 7.5 7.7 7.9

8 7.0 7.2 7.5 7.7 7.9 8.2

10 7.2 7.5 7.7 7.9 8.2 8.4

12 7.5 7.7 7.9 8.2 8.4 8.6

14 7.2 7.5 7.7 7.9 8.2 8.4

16 7.0 7.2 7.5 7.7 7.9 8.2

18 6.7 7.0 7.2 7.5 7.7 7.9

20 6.5 6.7 7.0 7.2 7.5 7.7

22 6.3 6.5 6.7 7.0 7.2 7.5

24 6.0 6.3 6.5 6.7 7.0 7.2

25 6.2 6.4 6.6 6.9 7.1 7.3

*50 or less.


61

TABLE 25

DESIGN METHODS AND CRITERIA FOR COARSE AGGREGATE HOT MIX BASE COURSES

A. Hveem Method

Percent Voids Percent Filled With

State Stability Air Voids Asphalt Cohesiometer

California 35 minimum 4-6

Colorado 30-45 3-5 80-85

Hawaii 35 minimum 5-10 75 300 minimum

Nevada 30-37 mln. 3-5

Oklahoma 35 minimum 8 maximum

Oregon 30 minimum 10 maximum 150 minimum

Texas 30 minimum Washington 20 minimum

B. Marshall Method

Percent Voids Stability Flow Value Percent Filled With

State lbs. 0.001 in. Air Voids Asphalt

District of Columbia 750 minimum 8-16 3-8 65-75

Georgia 1800 minimum 8-16 3-6 65-75

Kansas 800-3000 5-15 1-5 70-85

Kentucky 1100-1500 12-15 4-6

Mississippi 1600 16 maximum 5-7 50-70

New Jersey 1100-1500 6-18 3-7

N. Carolina 800 7-14 3-8

N. Dakota 400 minimum 8-18 3-5

Pennsylvania 700 minimum 6-16 60-85

Rhode Island 750 minimum 3-8

S. Carolina 1200-3000 6-12

S. Dakota 8-18 3-5

Wyoming 100 minimum

C. Unconflned Compressive Strength

State Load, psi Percent

Air Voids

Percent Voids Filled With Asphalt

Colorado

Oregon

200-400

150 minimum

3-5 80-85

[after Highway Research Board (13)]

62

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asphalt content determined by the Marshall method should be altered

depending upon the Pavement Temperature Index and the Traffic Area

(Table 27). Howver, these criteria were developed for surface

courses and do not appear to be warranted for base courses.

The Asphalt Institute (36) recommends three popular criteria for use

in hot-mix base course design (Table 28). Specifically, the Asphalt

Institute recommends the same criteria that are utilized for surface

courses, but the test temperature is 100oF rather than 140oP. This

recommendation applies to regions having climatic conditions similar to

those prevailing throughout most of the United States and provided the

base is A inches or more below the surface. Existing Information sug-

gests that most base courses at this depth do not reach a temperature

in excess of 100SF, and, therefore, the 100oF testing temperature

has been selected.

Zoepf (cited in reference 37) has also recommended Marshall criteria

baaed on studies conducted in Germany (Table 29).

McDowell and Smith (38) have recently presented a design procedure

based on unconfined compressive strength and air voids criteria for

the selection of the asphalt content. This method Includes the effect

of the rate of loading on the properties of asphalt treated materials.

Recent attempts have been made to develop a more rational approach

to pavement design. Among others. Monlsmith (39, 40) has indicated

that "elastic" properties and fatigue properties of the asphalt

treated base courses should be considered in pavement design. Testing

methods have been developed to measure these properties (41, 42, 43, 44)

and should be considered for possible utilization by the Air Force.

The above mentioned tests are generally considered as a measure of

64

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65

TABLE 28

MIXTURE DESIGN CRITERIA

A. Marshall Design Criteria

1 Traffic Category Heavy Medium LlBht 1 Test Property Min. Max. Min. Max. Min. Max. 1

No. of Compaction Blows | Each End of Specimen 75 50 35 |

Stability, all mixtures 750 — 500 500

Flow, all mixtures 8 16 8 18 8 20

Percent Air Voids 1 Surfacing or Leveling

Base 3 5 3 8

3 5 3 8

3 5 f 3 8

Percent Voids in Mineral ; Aggregate

B. Hveem Design Criteria

1 Traffic Category Heavy Medium Light 1 Test Pro£erty Min. Max. Min. Max. Mln. Max. 1

Stabllometer Value 37 — 35 30 1

Coheslometer Value 50 50 50

Swell less than 0.030 inch |

C. Hubbard-Field Design Criteria

Traffic Category Heavy Medium and Light Test Property Min. Max. Min. Max.

Stability-Pounds

Percent Air Voids

2,000

11 5%

1,200 2,000

2% 5%

Hot-mix asphalt bases, which do not meet the above criteria when tested at 140oF., should be satisfactory if they meet the criteria when tested at 100oF. and are placed 4 inches or more below the surface. This recommendation applies only to regions having climatic conditions similar to those prevailing throughout most of the United States. Guidelines for applying for the lower test temperature in regions having more extreme climatic conditions are being studied.

[after The Asphalt Institute (36)]

66

TABLE 29

MARSHALL MIX DESIGN CRITERIA

FOR ASPHALT CEMENT TREATED BASE COURSE

| Marshall | Requirement

at 140oF

Traffic, Vehicles per day 1

Light ( less

than 3000) Medium '

a000-3000) Heavy

(3000-6000 )

Extra Heavy (greater 1 than 6000

Stability, min.

Flow (0.01 In.)

Percent air voids

330

4-20

2-15

440

4-18

2-15

550

4-16

3-12

660 |

4-14 i

3-10

[after Zoepf as cited In (37)]

TABLE 3Ü

MARSHALL MIX DESIGN CRITERIA FOR

CUTBACK AND EMULSIFIED ASPHALT MIXTURES

| Marshall Test

Criteria for a Test Temperature of 770F|

Minimum Maximum 1

Stability, lbs.

Flow,(0.01 in.)

Percent air voids

750

7

3

16 1

5

[after Lefebvre (49)]

67

strength of asphalt-aggregate mixtures. A durability test should also

be considered to evaluate these mixtures. Tests which could be used

to measure durability Include the Immersion-compression test (13), the

swell test (36) and the Moisture Vapor Susceptibility (MVS) test (24).

Numerous laboratory tests have been used to determine asphalt

contents for cutback and emulsified asphalts. These methods Include:

1. Hubbard-Field Test, ASTM D1138-52 (45)

2. Hveem Stability, ASTM D1560-65 (46, 47)

3. Marshall Stability, ASIM D1559-65 (46, 46, 49)

4. Florida Bearing Test (50)

5. Iowa Bearing Test (51)

6. Extrusion Test, ASTM D915-61 (30, 46)

7. Unconfined Compression Test (45, 46, 52, 53, 54, 55)

8. Triaxial Compression Test (45)

9. "RM Value (20, 56, 57)

10. Elastic Modulus (20, 43, 57)

Mixing methods, curing conditions, rate of loading, and temperature

are important variables that must be carefully controlled when the

above mentioned tests are performed.

The most promising tests for utilization by the Air Force Include

the Marshall, Hveem and Extrusion tests. Criteria for the Marshall

and Hveem tests have been developed by several investigators and are

shown In Tables 30 and 31, respectively. The Air Force is presently

recommending use of the Extrusion Test (30) for mixture design with

the following criteria used for acceptability:

1. extrusion value before absorption - 1000 lbs. minimum

2. extrusion value after absorption - 400 lbs. minimum

68

Ml

TABLE 31

HVEEM MIX DESIGN CRITERIA

EMULSIFIED ASPHALT MIXTURES

Reference Criteria 1

Resistance Value Moisture Pickup During MVS, per cent Before MVS* After MVS*

Asphalt Institute (19) 70 min. 60 mln. —

Chevron Asphalt Company (20) —_— 70**, 78*** 5.0 max.

Finn, et al. (57) __* 70**, 73*** 5.0 max.

*Moisture Vapor Susceptibility **Light Traffic

***Heavy Traffic

TABLE 32

SELECTION OF A SUITABLE TYPE OF BITUMEN

FOR SOIL STABILIZATION PURPOSES

Crushed Stones and Sand Bitumen Soil Bitumen Sand-Gravel-Bitumen

Hot Mix: Hot Mix: Asphalt Cements Asphalt Cements

60-70 hot climate 40-50 hot climate 85-100 60-70 120-150 cold climate 85-100 cold climate

Cold Mix: Cold Mix: Cold Mix: Cutbacks Cutbacks Cutbacks See Figure 9 See Figure 9 See Figure 9

Emulsions Emulsions Emulsions See Table 19 See Table 19 See Table 19 See Figures See Figures See Figures 10 and 11 to 10 and 11 to 10 and 11 to determine if determine if determine if a catonlc or a catonlc or a catonlc or anonlc emulsion anonlc emulsion anonlc emulsion should be used should be used should be used

69

^r*™™*wmm&wm-mi*ejmM*mmtuM0mm»mmmam&iimmmmmm

3. expansion during absorption test - 5 percent maximum

The unconfined compression test Is easy to perform, but sufficient

experience to determine adequate criteria for Its use Is not available,

c. Methods based on combination of laboratory tests on soil and

soil-asphalt mixture

In these methods, selection of the quantity of bitumen for

stabilization Is usually based on preliminary estimates gained by

performing tests on the soil. One example is the Hveem method used

in California and several western states. Preliminary asphalt

content is based on CKE tests, and the final asphalt content is

selected on the basis of tests with the Hveem Stabllometer.

Finally, it should be mentioned that the use of elastic modulus for

the determination of asphalt content and as Input for pavement design has

been suggested by Terrel and Monlsmlth (43), Finn et al. (57) and Karl (58).

Pavements have been designed using these methods, and the Air Force should

give consideration to this testing method since research in pavement design

being conducted by the Air Force requires these Inputs.

4. Methods of Evaluating Bitumen-Soil Mixtures

The methods used for evaluating bituminous soil mixtures are Identical

to those used to select the asphalt content. It is Important to note that

not only are strength or stability criteria necessary, but also durability

criteria are recommended by most agencies. Typical examples of these tests

are the immersion-compression test utilized by Winterkorn (14) and by Rlley

and Blomqulst (55), and the MVS test utilized by the Chevron Asphalt Com-

pany (20), the Asphalt Institute (56) and Finn et al. (57).

70

5. Summary of Criteria for Bituminous Stabilization Subsys :ea

Criteria for the bituminous stabilization subsystem of the expedient

and nonexpedlent soil stabilization index system are given below:


A. Sobgrade

1. Selection of bitumen type

a. Do not use asphalt cements b. From the gradation of the soil determine if a soil

bitumen, sand bitumen, crushed stone bitumen, or sand-gravel bitumen (Table 7) can be constructed

c. Use Table 32 to select the type of asphalt

2. Selection of the quantity of bitumen

a. For cutback asphalts use the following equation recommended by the Asphalt Institute (16) and the Navy (22):

p - 0.02 (a) + 0.07 (b) + 0.15 (c) + 0.20 (d) where:

p ■ percent of residual asphalt by weight of dry aggregate


b ■ percent of mineral passing No. 50 and retained on No. 100 sieve

c - percent of mineral aggregate passing No. 100 and retained on No. 200 sieve

d = percent of mineral aggregate passing No. 200 sieve

b. For emulsions use Table 24 suggested by the Navy (22)

3. Method of evaluating mixtures

No testing is required

B. Base course


a. From the gradation of the soil determine if a soil bitumen, sand bitumen, crushed stone bitumen, or sand-gravel bitumen (Table 7) can be constructed

b. Use Table 32 to select the type of asphalt


71

TABLE 33

SELECTION OF ASPHALT CEMENT CONTENT

FOR EXPEDIENT BASE COURSE CONSTRUCTION

Aggregate Shape and Surface Texture

Percent Asphalt by Weight j of Dry Aggregate*

Rounded and Smooth

Angular and Rough

Intermediate

4 !

6

5 !

*Approximate quantities which may be adjusted in field based on observation of mix and engineering judgment

TABLE 34

DETERMINATION OF ASPHALT GRADE FOR

BASE COURSE STABILIZATION

1 Pavement Temperature Index* Asphalt Grade, Penetration !

Negative

! 0-40

40-100

Above 100

100-120 |

85-100

60-70

40-50

*The sum, for a 1- year period, of the increments above 750F of monthly averages of the daily maximum temperatures. Average dally maximum temperatures for the period of record should be used where 10 or more years of record are available. For records of less than 10- year duration the record for the hottest year should be used. A negative index results when no monthly average exceeds 750F. Negative indexes are evaluated merely by subtracting the largest monthly average from 750F.

72

TABLE 35

DETERMINATION OF QUANTITY OF CUTBACK ASPHALT

p - 0.02 (a) + 0.07 (b) + 0.15 (c) + 0.20 (d)

where: p = percent of residual asphalt by weight of dry aggregate.

a = percent of mineral aggregate retained on No. 50 sieve.

b = percent of mineral aggregate passing No. 50 and retained on No. 100 sieve.

c - percent of mineral aggregate passing No. 100 and retained on No. 200 sieve.

d ■ percent of mineral aggregate passing No. 200 sieve.

73

IMMM *x«iVMaNWMC

a. For cutback asphalts use equation recommended by the Asphalt Institute (16) and the Navy (22) given above

b. For emulsions use Table 24 suggested by the Navy (22) c. For asphalt cement use Table 33


No testing Is required

II. Nonexpedlent construction

A. Subgrade


a. Do not use asphalt cement (If asphalt cement is to be used a hot-plant must be available and usually a base course rather than a subgrade Is constructed)

b. From the gradation of the soil determine If a soil bitumen, sand bitumen, crushed stone bitumen or sand-gravel bitumen can be constructed

c. Use Table 32 to select the type of asphalt


a. For cutback asphalts use the following recommended by the Asphalt Institute (16) and the Navy (22) for a preliminary estimate:

P = 0.02 (a) + 0.07 (b) + 0.15 (c) + 0.20 (d) where:

p = percent of residual asphalt by weight of dry aggregate

a ■ percent of mineral aggregate retained on No. 50 sieve

b = percent of mineral aggregate passing No. 50 and retained on No. 100 sieve

c ■ percent of mineral aggregate passing No. 100 and retained on No. 200 sieve

d " percent of mineral aggregate passing ; No. 200 sieve

Use criteria developed by Lefebvre (Table 30) (49) for final selection of cutback content

b. For emulsion use Table 24 suggested by the Navy for preliminary selection. For final selection use criteria developed by Lefebvre (Table 30) (49). (Note that Lefebvre did not Intend these criteria to be used on emulsified asphalt treated soils.)


Use tests required above together with a suitable durability test. A suitable durability test or

74

criteria has not been selected

B. Base course


a. From the gradation of the soil determine If a soil bitumen, sand bitumen, crushed stone bitumen, or sand-gravel bitumen can be constructed

b. Use Table 32 to select the type of asphalt


a. For cutback asphalts use equation recommended by the Asphalt Institute (16) and the Navy (22) given above for preliminary estimate. Use criteria developed by Lefebvre (Table 30) (49) for final selection of cutback content

b. For emulsion use Table 24 suggested by the Navy for preliminary selection. For final selection use criteria developed by Lefebvre (Table 30) (49)

c. For asphalt cements use Table 33 on a preliminary basis. Use criteria developed by the Corps of Engineers for binder course (Table 26) (2) for final selection of asphalt content

3. Methods of evaluating mixtures

Use tests required above together with a suitable durability test. A suitable durability test or criteria has not been selected.

An effort has been made in the selection of the above criteria to con-

form to existing test methods and testing apparatus that the Air Force is

using on a routine basis. It is felt that more experience has been obtained

with the Hveem test method than others, but the Air Force does not possess

this equipment. The Asphalt Institute (56) and Chevron Asphalt Company (20),

among others, have extensive field data on mixtures designed with Hveem

test criteria as given in Tables 25, 28 and 31. For this reason, as well as

the inclusion of a durability test (MVS), the Air Force should consider this

mixture design method for possible future use. Additionally, the utilization

of the elastic modulus for pavement and mixture design should be considered.

' The above mentioned criteria have been used for the preparation of the

75

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struction operations shown in Figures 12, 13, 14 and 15, respectively.

76

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80

SECTION V

DESIGN SUBSYSTEM FOR PORTLAND CEMENT STABILIZATION

1. Introduction

Numerous technical papers and construction guides have been published

on portland cement stabilization (see reference 59, for example). These

papers contain criteria which will be reviewed In this section of the report

In order to develop the design subsystem for cement stabilization. For

convenience these criteria are separated Into the following categories:

a. selection of appropriate soils

b. selection of the type of cement

c. selection of the quantity of cement

d. methods of evaluating soil-cement mixtures

These criteria are discussed below.

2. Selection of Appropriate Soils

Information as to general requirements such as gradation and plasticity

Index have been discussed previously. Most research and construction with

soil-cement mixtures has been performed on soils which have been classified

according to the AASHO Classification System. Experience has shown that this

approach gives good results, but It does not Include the Important soil

properties such as clay type, soll pH, organic content and soil sulfate

content that may Influence the suitability of a soil for cement stabilization.

81

Research conducted by the Road Research Laboratory (60) (Figure 16) has

Indicated a general trend of Increased unconflned compresslve strength with

Increased soll pH. For soils with a pH value greater than 7, no 111 effects

on strength were noted. (Research conducted by Thompson (61) has Indicated

that a minimum soll pH of 7 Is also desirable for lime stabilization.)

Research has been conducted by the Portland Cement Association (62, 63)

on the utilization of the standard colorimetrlc test for the Identification

of organics, and the pH test on soils to indicate the reactivity of soil and

cement. No satisfactory correlation was found. The calcium adsorption test,

however, (62) is adequate to determine the presence of organics In sandy

soils i Maclean and Sherwood (60) also Indicated that the calcium adsorption

test was suitable for sandy soils, but that it was unsuitable for clay

soils. This opinion is shared by the Portland Cement Association (63).

A satisfactory method for determining the presence of active organic

matter is a pH test conducted on a soil-cement paste (10:1 mixture) after 15

minutes. Normal hardening of soil-cement will not occur if the pH of the

soil-cement paste has a value below 12 (60). The pH test on the soil-cement

mixture Is Intended to determine the reactivity of a soil with cement. This

reactivity is not solely a function of the organic content (62, 64)» but it

is also dependent upon the types of organics (65). It should be realized

that the pH tests performed by the Portland Cement Association (63) were

conducted on the soil and not the soil-cement mixture, and therefore

extensive data on the latter test are not available.

Sulfates present in the soils and the waters which may come in contact

with soil-cement mixtures have a detrimental effect on soil-cement strength.

Studies conducted by Sherwood (66) have indicated that sulfate contents in

82

es w 04 1-1 « o a

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600

S00

400

300

200

100

54

• <'

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54

i —«-• f—

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40 50 fco 70 80 90

SOIL pH

FIGURE 16. Effect of soll pH value on the unconflned compressive strength of soil cement mixtures

[after Maclean and Sherwood (60)]

83

soils In excess of 0.5 to 1.0 percent reduce the strength of soil-cement

mixtures. Similarly, soil-cement mixtures Immersed In water containing

sulfate concentrations exceeding 0.2 percent resulted in strength loss.

3. Selection of the Type of Cement

The Influence of the type of cement on the properties of soil-cement

mixtures has been examined by several investigators (66, 67, 68, 69). These

studies Indicate that only small differences can be expected between Types

I, II, III and V cements for most soils. Thus, it is recommended that

Type I cement be routinely used for soil-cement. However, if it is not

available and other types are, they may be used with no detrimental effects

expected. Specifications for cements are given in Table 36 (70).

4. Selection of the Quantity of Cement

Research performed by the Portland Cement Association, presented in

Highway Research Board publications (71, 72, 73) and summarized in the Soil-

Cement Laboratory Handbook (10), sets forth data for use in determining

cement contents for various types of soils. These cement requirements are

based on tests performed on over two thousand soils (10), and therefore

should be considered to be reliable.

The cement requirements for subsurface soils can be obtained from

Table 37. These criteria are based on the AASH0 Classification System, but

the Air Force has converted this classification for their use as shown in

this table.

Requirements for soils in various horizons are also specified by the

Portland Cement Association (Tables 37, 38 and 39). It should be noted that

estimates of cement content for B and C horizon soils are dependent upon the

84

TABLE 36

SPECIFICATIONS FOR PORTLAND CEMENT

Physical Requirements

Type I Type II Type III Type IV Type V

Fineness specific surface, sq en per g (alternate methods):

Turbldlmeter test: Average value, mln Minimum value, any one sample

Air permeability test: Average value, mln Minimum value, any one sample

Soundness: Autoclave expansion, max, percent

Time of setting (alternate methods): Glllmore test:

Initial set, mln, not less than Final set, hr, not more than

Vicat test (Method C 191): Set, mln, not less than

Air content of mortar, prepared and tested in accordance with Method C 185, max, percent by volume, less than

Compresslve strength, psi: The compresslve strength of mortar cubes, composed of 1 part cement and 2,75 parts graded standard sand, by weight, prepared and tested in accordance with Method C 109, shall be equal to or higher than the values specified for the ages indicated below:

1 day in moist air 1 day in moist air, 2 days In water 1 day in moist air, 6 days in water 1 day in moist air, 27 days In water

Tensile strength, pal: The tensile strength of mortar briquets composed of 1 part cement and e parts standard sand, by weight, prepared and teated in accordance with Method C 190, shall be equal to or higher than the values specified for the ages indicated below:

1 day in moist air 1 day in moist air, 2 days in water 1 day in moist air, 6 days in water 1 day in moist air, 27 days in water

Heat of hydration: 7 days, max, cal pet g 28 days, max, cal per g

1600 1500

2800 2600

0.80

1600 1500

2800 2600

0.80 0.80

1600 1500

2800 2600

0.80

.1600 1500

2800 2600

0.80

60 60 60 60 60 10 10 10 10 10

45

12.0

45

12.0

45

12.0

45

12.0

45

12.0

1700 1200 1000 3000 2100 1800 800 1500 3500 3500 2000 3000

275 150 125 375 275 250 175 250 350 325 300 325

——— 70 80 _...

———— ::::

Chemical Requirements

Type I Type II Type III Type IV Type V

Silicon dioxide (SIO2), mln, percent Aluminum oxide (AI2O3), max, percent

21.0

6.0 6.5 5.0 5.0 5.0 5.0 4.0

2.5 2.5 3.0 2.3 2.3 3.0 4.0 3.0 3.0 3.0 2.3 3.0 0.71 0.75 0.75 0.75 0.75

8 15 7 5

Masneslum oxide (MttO). max. percent Sulfur trioxide (803), max, percent

When 3Ca0-Al2O3 is more than 8 percent Loss on ignition, max, percent Insoluble residue, max, percent Tricalcium silicate (3CaO'Si02), max, percent Dicalcium silicate (3Ca0'Si02), max, percent Tricalcium aluminate (3Ca0.Al203), max, percent Sum of tricalcium silicate and tricalcium

(after ASTM (70)1

85

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86

TABLE 38

AVERAGE CEMENT REQUIREMENTS OF B AND C HORIZON SANDY SOILS

Material fwQIIMO 9R No. 4 Ovn,

ptrnnl

tnoltcr than

0.05 mm., par cant

Ccnwnl cantonl, p*r ctnl by wf.

105-109 110-114 Maximum density, lb. par cu.fl.

115-119 | 120-134 125-129 130 or men

0-14 0-19

20-39 40-50

10 9

11 10

15-29 0-19

20-39 40-50

10 9

12 10

3(M3 0-19

20-39 40-50

10 11 12 11 10


TABLE 39

AVERAGE CEMENT REQUIREMENTS OF B AND C HORIZON SILTY CLAYEY SOILS

111

Comonl content, por ctnt by wt.

AASHO and Maximum domity, lb. ptr cu.fl. group 0.005 mm., Indox par cont 90-94 95-99 100-104 105-109 110-114 115-119 120 or mort

0-19 11 10 t 8 20-39 11 10 9 8

0-3 40-59 12 11 9 9 60 or moro — — — — — —

0-19 12 11 9 8 20-39 12 11 10 9

4-7 40-59 13 12 10 10 60 or moro 14 12 11 10

0-19 13 11 10 9 20-39 14 11 10 9

a-ii 40-59 14 12 11 10 60 or moro 15 13 11 10 10

0-19 14 13 12 11 20-39 15 13 12 11

12-15 40-59 16 14 12 12 60 or moro 16 14 13 12

0-19 16 14 13 12 20-39 17 15 14 13

16-20 40-59 18 15 14 14 60 or moro 20 19 16 15 14

[after Portland Cement Association (10)1

87

density of a soil-cement mixture having a cement content specified in Table

37. Average cement requirements for miscellaneous materials are shown in

Table 40.

A systems approach to the determination of cement requirements for

soils has been presented by the Portland Cement Association (Figure 17) (73).

Since these test methods are based on over 30 years of experience, their

adoption (at least in part) Into the Air Force stabilization index system

Is recommended. It should be noted that criteria and test methods exist for

small and emergency projects (Figure 17) which would be suitable for the

expedient construction practice requirements of the Air Force. Detailed

information on this approach can be found In reference 73. The Portland

Cement Association methods have been adopted in part by the Navy (75) , the

Army and the Air Force (2).

An additional short-cut method has been proposed by Diamond and Kinter

(76). This method makes use of a correlation between the surface area of a

soil measured by the glycerol retention test (77) and the cement requirement.

A flow diagram for the proposed use of this method is shown in Figure 18.

5. Methods of Evaluating Soil-Cement Mixtures

Various types of tests have been used to evaluate the properties of

soil-cement mixtures (59). These methods Include the following:

a. Unconflned Compresslve Strength

b. Flexural Strength

c. Modulus of Elasticity

1. Static in Flexure

2. Static In Compression

3. Resonance Modulus

88

■■ MMiui» MOM ■■-■■.

TABLE 40

AVERAGE CEMENT REQUIREMENTS

OF MISCELLANEOUS MATERIALS

EtHmatad cement content and that Cement contents

Typ««» used in for wet-dry and freeie-lhaw

imranyi tctt teltif par cent by wt. per cent per cent

by vol. by wt.

Shall Milt S 7 3- 7- 9 Umatlon« Kr««ntngt 7 5 3- 5- 7 Rad dog 9 8 6- 8-10

thala 11 10 8-10-12 Calicha 8 7 i- 7-9 Cindart 8 8 6- 8-10 Chart 9 8 6- 8-10 Choi 8 7 5-7. 9 Marl 11 11 9-11-13 Scoria containing ma-

tarial rttaintd on the No. 4 >l«v* 12 11 9-11-13

Scoria not containing matarial retained on the No. 4 ileve 8 7 J. 7- 9

Air-cooled tiag 9 7 3-7.9 Water-cooled liag 10 12 10-12-14


89

.f '■'

MAJOR PROJECTS

SOIL SAMPLING AND PREPARATION

SOIL IDENTIFICATION TESTS

Sandy soils Soils of all textures

SHORT-CUT TEST METHOD

1 Moisture-density test 2 Determination of cement

requirement by charts. 3.Compressive-strength test.

VERY SMALL AND EMERGENCY PROJECTS

SOIL SAMPLING AND PREPARATION

COMPLETE SERIES OF DETAILED TESTS

I.Moisture-density test. 2Wet-dry 8i freeze-thaw tests 3.Compressivestrength tests.

METHOD FOR SOILS IDEN TIFIED BY SOIL SERIES

Use cement factor determined by previous tests on this series.

RAPID TEST METHOD

I.Moisture-density test. 2>ick'and'click'tests

FIGURE 17. SOIL-CEMENT LABORATORY TESTING METHODS


90

DETERMINE GRAIN SIZE DISTRIBUTION AND ATTERBERG TEST LIMITS OF SOIL

I INON-PLASTIC SOILSl

SOILS WITH LESS THAN 45% SILT

THIS METHOD NOT APPLICABLE (USE T-136-57 OR PCA SHORT CUT METHOD)

| PLASTIC SOILSl 1

SOILS WITH 45% OR MORE SILT

X THIS METHOD NOT APPLICABLE

(USE AASHO T-136-57)

[DETERMINE SURFACE AREA BY GLYCEROL RETENTION PROCEDURE!

FROM REGRESSION EQUATION Y=0.087(SURFACE AREA)+3.79,CALCULATE Y, AN ESTIMATE OF WEIGHT % OF CEMENT AT WHICH 10% LOSS WOULD OCCUR IN 12 CYCLE FREEZE-THÄW TEST

A-l,A-2-4,A-2-5 SOILS I

A-2-6,A-2-7,A-4,A-5 SO LS

SUBTRACT 0.7 TO CORRECT'Y FOR 14% ALLOWABLE LOSS

1 A-6,A-7

SOILS i.

ADD 2.0 TO CORRECT"Y FOR 7% ALLOWABLE LOSS

I DETERMINE MAXIMUM DENSITY AND OPTIMUM MOISTURE

CONTENT OF SOIL-CEMENT MIXTURE AT THIS CEMENT CONTENT

I CALCULATE CEMENT REQUIREMENT, PERCENT BY VOLUME,FROM

PERCENT BY WEIGHT VALUE AND MAXIMUM DENSITY

I MOLO COMPRESSIVE STRENGTH SPECIMENS AT INDICATED CEMENT CONTENT AND ±2%1AN0 TEST TO INSURE SATISFACTORY HARDENING

FIGURE 18. Flow diagram for short-cut method using surface area

to determine cement requirements

[after Diamond and Klnter (76)]

91

4. Dynamic

d. California Bearing Ratio

e. Plate Bearing Value

f. Fatigue

g. "R" Value

h. Freeze-Thaw

i. Wet-Dry

Since many of these methods have not been used extensively, satisfactory

criteria are not available. However, some tests are being used on a routine

basis and criteria have been developed.

Freeze-thaw and wet-dry requirements set forth by the Portland Cement

Association (10) are shown In Table 41. These requirements apply to base

course construction. It is suggested that freeze-thaw and wet-dry criteria

not be used for subgrade stabilization evaluation (63).

Typical unconfined compresslve strengths that can be expected for

common soil types are shown In Table 42. Unconfined compresslve strength

criteria used by various agencies are shewn in Table 43. The Portland Cement

Association specifies minimum compresslve strengths for sand-soll-cement

mixtures designed by the Short-Cut Methods. These criteria are shown in

Figures 19 and 20. These procedures should only be used with soils containing

less than 50 percent of particles smaller than 0.05 mm (silt) and less than

20 percent smaller than 0.005 mm (clay).

Criteria dependent on other types of tests are not sufficiently

developed to yield reliable data.

6. Summary of Criteria for Cement Stabilization Subsystem

Criteria for the Cement Stabilization Subsystem of the Expedient and

92

TABLE 41

PORTLAND CEMENT ASSOCIATION CRITERIA FOR

SOIL-CEMENT MIXTURES USED IN BASE COURSES

Soil Classification Soil-Cement Weight

Loss During 12 Cycles of Either Wet-Dry Test

or Freeze-Thaw Test AASHO Unified*

A-1

A-2-4, A-2-5

A-3

GW, GP, GM SW, SP, SM

GM, GC, SM, SC

SP

less than or equal to 14 percent

A-2-6, A-2-7

A-4

A-5

GM, GC, SM, SC

CL, ML

ML, MH, OH


A-6

A-7

CL, CH

OH, MH, CH less than or equal to 7 percent

♦based on correlation presented by Air Force (2)


93

IWI«l«lt»BKrär-K-:lW|«lfJBaft»W?

TABLE 42

RANGES OF UNCONFINED COMPRESSIVE STRENGTHS OF SOIL-CEMENT

j Soil Type Wet Compressive Strength0(psi) 1

7-Day 28-Day j

Sandy and gravelly soils: AASHO groups A-l, A-2, A-3 Unified groups GW, GC, GP, GF, SW, SC, SP, SF 300-600 400-1,000

Silty soils: AASHO groups A-4 and A-5 Unified groups ML and CL 250-500 300-900

Clayey soils: AASHO groups A-6 and A-7

| Unified groups MH and CH 200-400 250-600

Specimens moist cured 7 or 28 days, then saturated in water prior to strength testing.

[after Highway Research Board (59)]

TABLE 43

UNCONFINED COMPRESSIVE STRENGTH CRITERIA FOR SOIL-CEMENT MIXTURES

Agency Unconflned Compressive

Strength, psi

Curing Age, Days

California - Class A&B CTB (ref. 24) 750 7 |

Texas (ref. 77) 700 7

Road Research j Laboratory (ref. 60) 250 7 1

Air Force (ref. 2) 300 7

94

t'Wv**miK*e>*amimmmimm*iim>*-'. - m-

bO—i

40-

E E m O O

= 20- o E

10-

— 30

o

o - S

45

•40

20

*— 0

FIGURE 19. Minimum 7-day compressive strengths required for soil-cement mixtures containing material retained on the No. 4 sieve.*


*these strength requirements are applicable provided the soil has the following gradation: <50% smaller than 0.05 mm (silt)

<20% smaller than 0.005 mm (clay)

95

m M

a f-

8|250

ll S 200

^ ̂ ^

i i 1 1 MM

\ ̂ ^

MM i 1 1 1 MM MM 1 1 1 1 MM MM i i i i 15 20 25 20 35 Material sn.aller than 005 mm.- per cent

40 45 50

FIGURE 20. Minimum 7-day compressive strengths required for soil-cement mixtures not containing material retained on the No. 4 sieve.*


* these strength requirements are applicable provided the soil has the following gradation: <50% smaller than 0.05 mm (silt)

<20% smaller than 0.005 mm (clay)

96

^AAW^J«^^»^^^^^ -

Nonexpedlent soll stabilization Index system are given below.


A. Subgrade

1. Selection of soil type

No additional requirements are recommended

2. Selection of cement type

Use Type I Portland Cement

3. Selection of cement content

Use values selected by Portland Cement Association (Table 37) (10)

4. Methods of evaluating mixtures

Use Rapid Test Procedures recommended by Portland Cement Association (10) shown in Appendix E

B. Base course

These criteria are identical to those listed above for the subgrade

II. Nonexpedlent construction

A. Subgrade

1. Selection of soil types

a. Use British test which requires the pH of a 10:1 soil-cement mixture to be 12.0 or greater after 15 minutes (Appendix F)

b. Determine presence of sulfates and require soil to have less than 0.90 percent sulfate content (as SO ) (Appendix G)


Use Type I Portland Cemen


a. If the soil is sandy as defined by the Portland Cement Association, use the short-cut methods recommended by the Portland Cement Association (Appendix H) (10)

b. If the soil is not sandy, use the procedures recommended by Portland Cement Association

97

(Appendix I) (10), but do not perform the wet- dry and freeze-thaw tests

c. Specimens molded at the selected cement content should pass the "pick" and "click" test given in Appendix E


Use those tests required in 3. above

B. Base course

1. Selection of soil types

a. Use British test which requires the pH of a 10:1 soil-cement mixture to be 12.0 or greater after 15 minutes (Appendix F)

b. Determine presence of sulfates and require soil to have less than 0.90 percent sulfate content (as SO.) (Appendix G)


Use Type I Portland Cement


a. If the soil is sandy as deH ted by the Portland Cement Association, use the short-cut methods recommended by the Portland Cement Association (Appendix H) (10)

b. If the soil is not sandy, use the procedures recommended by Portland Cement Association (Appendix H) (10) and the criteria shown in Table 41 (10)


Use those tests required in 3. above

Design subsystems for Expedient and Nonexpedlent construction operations

are shown in Figures 21, 22, 23 and 24. These subsystems are based on the

above criteria.

98

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■

SECTION VI

DESIGN SUBSYSTEM FOR LIME STABILIZATION

1. Introduction

Numerous research publications and technical guides are available on

lime stabilization. The wide range of soils successfully stabilized with

lime attest to its effectiveness. Numerous criteria have been developed,

many of them based on experience with limited soil types. These criteria

will be reviewed in this section to develop the lime stabilization subsystem.

The following criteria are included:

a. Selection of lime type

b. Selection of appropriate soils

c. Guides to selection of lime quantity

These are discussed below.

2. Selection of Type of Lime

Lime is generally used as an all-encompassing term to denote either

slaked (hydrated) lime or quicklime. Also, there are two types of lime:

calcitic lime and dolomitic (high magnesium) lime (79, 80). The quality and

type of lime are dependent on many factors, including type of stone used,

size and gradation of stone, and chemical reactivity of stone, to name a few.

There Is some disagreement as to whether the type of lime influences the

strength of lime-soil mixtures. Some researchers have reported that dolomitic

limes produce higher strengths than calcitic limes (81) while others have

103

found that calcitic limes will produce shear strengths as high as dolomitic

limes and may be more desirable for stabilizing certain soil types (82).

In the Zone of Interior there may be a choice of limes, in which case It

could be economically beneficial to determine which type of lime will be

most reactive with the soil. However, in the Theater of Operations, the

engineer will use that material which Is available without respect to whether

it is dolomitic or calcitic, and there is no reason to expect detrimental

effects of one over the other.

Lime manufactured in foreign countries may not be as beneficial to

soils in the same quantities as U.S. manufactured material. It is not

usually subjected to as rigorous a quality control as portland cement or

bitumens, and its composition might vary from a single source as well as from

different sources. Quality control tests are available (83), but they require

equipment not ordinarily available in the Theater of Operations. For these

reasons, design tests should be performed using limes from the anticipated

sources, and frequent check tests should be made.

Quicklime is reported to have some major advantages over hydrated lime

(4):

a. In the treatment of wet soils, strength benefits will occur in

a matter of hours,

b. Significant drying effect of the soil will be achieved almost

immediately,

c. Less quicklime will be needed than hydrated lime.

However, quicklime can produce severe burns, particularly in hot, humid

climates, and adequate safety precautions must be observed.

Hydrated lime may also produce skin irritations.

Specifications for lime which is suitable for stabilization are shown

104

In Table 44 (84) .

3. Selection of Appropriate Soils

Section III discussed the general requirements of the soil with respect

to gradation and plasticity. However, there are other requirements which

must be considered as well, including organic content of soll, pH, type(s)

of clay mineral(s), presence of sulfates and possibly the horizon in which

the soil is located.

Thompson (85) has defined soils as being lime-reactive if they display

significant strength increase (measured by the unconflned compressive strength)

when treated with lime. Soils which are not lime-reactive according to this

definition are not necessarily unimproved by the addition of lime as it may

still decrease their plasticity, decrease their susceptibility to water, and

enhance their overall engineering behavior (86). However, since improved

load-bearing characteristics are desired in the stabilization Index system,

strength will be a major consideration herein.

Soils which have a pH greater than 7 are usually indicative of good lime

reactivity (85), although soils with pH values as low as 5.7 have reportedly

been effectively stabilized with lime.

It has been reported that soils with organic carbon exceeding about one

percent are not satisfactorily lime-reactive (85) . And the presence of

significant amounts of sulfates also diminishes the effectiveness of lime.

Thompson has reported that A-horlzon soils in Illinois do not satisfac-

torily react with lime (85) , and similar reports have been made on other

soils; this is probably the result of high organic contents in the upper

horizon and the lack of lime reactive constituents. Poorly drained soils

often are the most reactive to lime, possibly because of the higher pH and

105

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106

■

the availability of lime reactive constituents, such as unweathered soil

minerals.

In general terms, the soils which are most reactive to lime include

a. Clayey gravels

b. Silty clays

c. Clays.

In the AASHO soil classification system, the most suitable soils include

A-2-5, A-2-6, A-2-7, A-5, A-6 and A-7. These correspond generally to the

following soils classified by the Unified Soil Classification System: GC,

. GC-GM, SC, SC-SM, CL, ML, CH, MH. Some lime reactivity may be displayed by

GM, SM, and CL-ML soils, and by A-2-4 and A-4 soils.

For the most part, the low plasticity soils do not contain sufficient

lime reactive materials to produce significant increases in strength.

Thompson (87), however, has reported successful stabilization of some A-4

soils found in Illinois. The use of lime in base courses is not encouraged

because of cracking that has occurred in these elements (9). This is probably

the result of a certain amount of "tenderness" that occurs in low P.I. lime-

stabilized soils. Texas Highway Department experience (88) is that this

cracking can be reduced significantly if heavy traffic is kept off the stabilized

material for sufficiently long periods of time to allow adequate curing. If

a low-type flexible surfacing, such as a surface treatment can be used, then

the deleterious effect of cracking will be less serious. Cracking will be

reflected in the higher quality surfacings such as hot-mix asphaltlc concrete.

In general, the lime stabilized zone will vary with the type of traffic.

Lime may be best utilized in expedient construction in the upper layers,

particularly if the anticipated traffic Is low. In nonexpedlent construction,

the use of lime will usually be restricted to the lower layers of more plastic

107

;'-V;-v . mM*»* ■ —■ : •• • . ■

materials where cracking will not be a problem (88)•

4. Selection of Lime Quantity

There is less definitive criteria for evaluating the correct quantity

of lime than there is for cement or bitumens. Short-cut tests are almost

non-existent. As a rough guide the Corps of Engineers (89) has proposed

the information given in Table 45 for determining approximate lime contents.

Eades and Grim have proposed a test where the appropriate lime content

is that which will produce a pH of a lime-soil mixture of 12.4 one hour

after mixing (90). However, recent information has indicated that this test

may not be valid for certain highly weathered soils (87) .

Most authors have reported that a minimum of 3 percent lime is necessary

to produce adequate reactions in the field (86). The Air Force (30) suggests

that 2, 3 and 5 percent lime be tried in coarse soils (those containing 50

percent or less passing the No. 200 sieve) while 3, 5 and 7 percent be tried

for fine grained soils (greater than 50 percent passing the No. 200 sieve).

The National Lime Association recommends the use of 3, 5 and 7 percent lime In

trial mixtures (86). With the exception of the pH test described above, the

lime content must generally be determined by trial mixtures with the amount of

lime being the minimum required to produce the desired reactions.

5. Methods of Evaluating Soil-Lime Mixtures

Several types of tests have been proposed for evaluating soil-lime mix-

tures. These include, but are not limited to:

a. Unconfined Compressive Strength

b. California Bearing Ratio

c. Flexural Fatigue Strength

108

TABLE 45

APPROXIMATE LIME CONTENTS

Soil Type

Approximate treatment, percent bv soil weicht 1

Hydrated Lime Quicklime

Clayey gravels (GC, GM-GC) (A-2-6, A-2-7) 2-4 2-3

Silty clays (CL) (A-6, A-7-6) 5-10 3-8 1

Clays (CH) (A-6, A-7-6) 3-8 3-6 |


109

d. Triaxial Compressive Strength

e. Elastic Properties

f. Coheslometer Values

g. Freeze-thaw Tests

h. Wet-dry Tests.

Most of these tests are not used routinely, and satisfactory criteria are

not generally available. Some of the most reliable data are based on uncon-

fined compressive strengths developed from research done by Thompson (91),

and presented in Table 46. This table shows strength requirements for various

elements in pavements (base course, subbase, etc.) and is based on highway

loadings. Until similar data become available for airfield pavements, the

values in Table 46 should be considered as minimum values for airfields and

should be used with caution.

Durability, the ability of a material to retain stability and integrity

over years of exposure to weathering, is perhaps the most difficult to

determine. Of the many tests developed, only a modified freeze-thaw test

shows substantial merit (92) .

6. Summary of Criteria for Lime Stabilization Subsystem

Criteria for the Lime Stabilization Subsystem of the Expedient and

Nonexpedient soil stabilization index system are given below.

I. Expedient Construction

A. Subgrade


No additional requirements recommended»

2. Selection of lime type

Use available lime. 110

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3. Selection of lime content

a. Estimate approximate lime content (Table 45)

b. Use pH test (Appendix J) on mixtures containing

approximate lime contents and require mixture to

have pH greater than 12.4 after 1 hour.

4. Methods of evaluating mixture

No further tests required

B. Base course


No additional requirements recommended

2. Selection of lime type

Use available lime

3. Selection of lime content

a. Use pH test (Appendix J) on mixtures and determine

minimum lime content giving pH of 12.4 after 1 hour.

b. Mold unconfined compressive strength specimens on

mixture with minimum lime content

c. If lime produces strength increase greater than 50

psi, soil is lime reactive. Mold additional strength

specimens at + 2 percent lime to obtain optimum lime

content.

d. If lime produces strength increase less than 50 psi,

soil is not lime reactive and will not stabilize

with lime.

4. Method of evaluating mixture

Use unconfined compression specimens and compare

112

with criteria in Table 46.

II. Nonexpedlent Construction

A. Subgrade

These requirements are identical to those for

expedient base course given above.

B. Ba~.e course

These requirements are identical to those for

expedient base course given above.

The above criteria were used to develop the lime stabilization sub-

systems shown in Figures 25, 26, 27 and 28.

113

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SECTION VII

SELECTION OF CRITERIA FOR MECHANICAL STABILIZATION

1. Introduction

In recent years, the considerable volume of research on chemical soil

stabilization has glamorized this method to the extent that the older

stabilization methods are often forgotten. Yet, these older and logistically

more appealing methods may do the Job as well as chemical stabilization and

at a fraction of the cost. The methods being referred to here are densifica-

tlon (compaction) and blending. Both compaction and blending are part of the

construction sequence in chemical stabilization, thus much of the basic

equipment for the two different methods is identical.

Whether to use chemical or mechanical stabilization is a basic engineering

decision where there are no specific guide rules. In all probability, it Is

the difficulty of making this decision on a quantitative basis that has caused

many engineers to turn to chemical stabilization (which seems a more positive

method) and neglect mechanical means. It is not purported that this section

can provide means for making this decision, but it can provide some of the

questions which the engineer should ask when deciding which stabilization

method should be used. These are outlined below.

a. Strength

Will mechanical stabilization alone provide adequate strength, or will

it be necessary to use chemical additives? Compaction alone can result in

strength gains of 300 percent or more. Too often, engineers forget this

118

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fact and search for more sophisticated methods. The magnitude of

strength Increase available can be determined simply by CBR tests on

specimens compacted at various compactlve efforts In accordance with

procedures outlined In Technical Manuals TM 5-824-2 (25) and TM 5-824-3

(93). However, environmental factors must not be neglected,

b. Permanency of Strength

Will the strength gains by mechanical stabilization be permanent?

It Is here that the decision for chemical or mechanical stabilization

Is often made. Many soils will exhibit high strength gains when com-

pacted but they may lose a portion or all of this strength by various

means Including Infiltration of water from the surface or surrounding

soil, disrupting action of frost, and others. Information given In

Technical Memorandum No. 3-357 by the Waterways Experiment Station (94)

(Table 47) gives a very good estimate of the permanency of strength that

can be expected with various soils classified according to the Unified

Soil Classification System.

In many cases, certain construction procedures can be used to

maintain strength or decrease the rate of strength deterioration. For

example, a thin asphalt prime coat will Impede moisture movement Into a

the soil, at least from the surface. Enclosing the soil In an Imperme-

able membrane Is another means of maintaining the as-built strength.

The membrane material may be heavy plastic sheeting, low penetration

grades of asphalt cement or a combination of the two, usually with the

plastic sheeting on the underside of the enveloped layer and the asphalt

cement on the top side. Care must be taken to prevent rips in the

plastic or "holidays" in the asphalt cement coating, although for high

risk, short life, expedient operations (which this process seems well

119

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suited for) this may not be of paramount Importance.

c. Construction Weather

Will the cllmatologlcal conditions be suitable for mechanical

stabilization? Often the climate during the construction period will ■

be unsuitable. If the rainfall Is too high, then It may be Impossible

to dry the soil to a moisture content suitable for compaction. Also,

low temperatures retard evaporation and make It difficult to obtain the

correct moisture.

d. Construction Equipment Limitations

Will the available construction equipment be suitable for

mechanical stabilization? The compaction equipment available on the

project should be adequate to produce the high densities needed for

strength purposes. If not, then the hardening and/or binding effect of

chemical stabilizers may be needed. Insofar as blending is concerned,

It should be realized that attempts to blend small quantities of soils

In the laboratory for experimentation purposes are usually much more

successful than in the field. In general, until better mixing equipment

becomes available, blending should be used sparingly, and only within

the limitations imposed later in this section.

e. Material Logistics

If blending is necessary, will it be feasible, both from an economic

and time viewpoint? It may take only 5-7 percent clay to stabilize a

sand, whereas 90-95 percent sand may be needed to adequately stabilize a

clay. Obviously, the latter would not be feasible even if the sand

were nearby.

If the engineer determines that the strength of the mechanically

stabilized material will be adequate and of sufficient permanency for the

121

project at hand, and If the construction weather, construction equipment

and material logistics are favorable, then mechanical stabilization may be

used, subject to the requirements and limitations discussed below.

2. Compaction Requirements

The Corps of Engineers have developed compaction requirements for sub-

grades, subbases and base courses. These requirements are based on extensive

test track and full scale testing, and can be considered to be the best

presently available for airfield construction.

Compaction requirements for subgrades, subbases, and base courses for

flexible as well as rigid airfield construction are available In IM 5-824-2

(25) and TM 5-824-3 (93). Various Air Force manuals for airfields, roads,

etc., refer to these manuals.

Although the compaction requirements for flexible pavements are more

specifically given in IM 5-824-2 as shown In Table 48, a summary of the

requirements is presented below:

a. Base Course - excess of 100 percent of Modified AASHO

b. Subbase - 100 percent or greater of Modified AASHO

c. Subgrade

1. Coheslonless material - 100 percent Modified AASHO

2. Cohesive material - top portion greater than 95 percent

Modified AASHO

d. Fill Sections

1. Coheslonless materials - 95 percent Modified AASHO

2. Cohesive materials - 90 percent Modified AASHO

v As'shown in Table 48 the depth of densification for select material and

subgrade is dependent on the type of aircraft, type of materials and density

122

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required.

Compaction requirements for material under rigid pavements are given In

TM 5-824-3 (93). These requirements are summarized below:

a. Base Course

1. Thickness less than 10 Inches

95 percent Modified AASHO

2. Thickness greater than 10 Inches

top 6 Inches - 100 percent Modified AASHO

below 6 Inches - 95 percent Modified AASHO

b. Subgrade

1. Fill sections

1. Cohesive - 90 percent Modified AASHO

11. Coheslonless


below 6 Inches - 95 percent Modified AASHO

2. Cut sections

1. Cohesive


11. Coheslonless


18 Inches below top 6 Inches - 95 percent Modified AASHO

It Is emphasized that the above specifications do not ensure adequate

strength of the material, and that It will still be necessary to ascertain

that the material has adequate strength to resist the applied load.

124

3. Blending

Blending makes possible the use of materials which by themselves will

not meet existing specifications, but when blended In proper proportions will

provide a suitable material.

Gradation and Atterberg limits for select materials and subbases are

shown In Table 49 (25). If practical, suitable materials can be blended to

meet these specifications; however, local materials are often available which

will meet these criteria without requiring blending.

Gradation bands for combined materials to be used as base courses are

shown In Table 50. Atterberg limit criteria should also be Imposed to In-

sure proper blending of base course components. These criteria are presented

In Table 51 (95).

4. Special Considerations

in many instances, compaction and/or blending will provide a material of

Improved load carrying capacity. However, as mentioned earlier, this strength

Increase may not be permanent, and In some soils a high degree of denslflca-

tlon may be Injurious. These special considerations are discussed below.

a. Clays That Lose Strength When Remolded

The Individual particles In certain clay soils have a definite

structure. Destruction of this structural arrangement by the compaction

process - even at a constant water content - will greatly reduce the

strength of the material. The effect of remolding can be determined by

strength tests on In situ and remolded specimens. If the undisturbed

value Is higher then no compaction should be attempted.

b. Silts That Become Quick When Remolded

Some deposits of silt, very fine sand and rock flour (ML and SM soils)

125

TABLE 49

GRADING AND ATTERBERG LIMITS FOR

SELECT AND SUBBASE MATERIAL

Material

ftaxlmum Design

CBR

Maximum Permissible Value i

'Size ' Inches

Gradation Require- ments » percent

passing

« 1

Atterberg 1 Limits

No. 10 No. 200 "LL PI

Subbase 5'0 3 50 15 25 5

Subbase 40 3 80 15 25 5

Subbase 30 3 100 15 25 5

[select Material 20 3 25 35 12


126

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TABLE 50

DESIRABLE GRADATION FOR CRUSHED ROCK,

GRAVEL, OR SLAG, AND UNCRUSHED SANDY AND GRAVEL

AGGREGATES FOR BASE COURSES AND FOR MECHANICAL

STABILIZATION

Sieve designation

Percent passing each sieve (square openings) by weight

Maximum aggregate size

3-Inch 2-lnch 1 1/2-inch 1-inch 1-lnch

sand-clay

3-inch 2-lnch 1 1/2-lnch 1-lnch 3/4-lnch 3/8-lnch No. 4 No. 10 No. 40 No. 200

100 65-100

45-75

30-60 25-50 20-40 10-25 3-10

100 70-100 55-85 50-80 30-60 20-50 15-40 5-25 0-10

100 75-100 60-90 45-75 30-60 20-50 10-30 5-15

100 70-100 50-80 35-65 20-50 15-30 5-15

100

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TABLE 51

ATTERBERG LIMIT REQUIREMENTS FOR BLENDING

Type of Construction Atterberg Limit Requirements of Each Component

Plastic Index Liquid Limit

Normal

Theater of Operation

Emergency

5

10

15

25

36

45

[after U. S. Army (95)J

127

when compacted In the presence of a high water table will pump water to

the surface and become spongy with a significant loss of bearing value.

In such cases. It Is necessary to remove the source of water by lowering

the ground water table. If this is not feasible, then the subgrade

should not be disturbed and additional thicknesses of overlying better

material must be used.

c. Clays With Expansive Characteristics

In many parts of the world, soils exist which swell when they absorb

moisture and shrink when they dry. This may result in differential

heaving of pavements that Is Intolerable. If the amount of swell is

less than about 3 percent, special consideration will not normally be

needed (95) . A common way to treat such soils Is to compact them at a

moisture content and unit weight that will minimize expansion. A combi-

nation of moisture, density, CBR and swell which will give the greatest

CBR and density consistent with a tolerable amount of swell must be

selected. These will not necessarily be the optimum moisture content

and unit weight determined by the modified AASHO compaction test.

d. Soils That Are Frost Susceptible

Many soils found in colder regions of the world undergo significant

strength losses due to the action of frost. Pavements over these soils

are frequently broken up as subgrades freeze in winter and thaw In

spring. In particular, when the subgrades thaw in the spring they be-

come extremely unstable, and in some cases it may become necessary to

close a facility until the subgrade recovers its stability. The design

of pavements in frost areas is a special procedure which is presented

elsewhere (96). However, since frost susceptible soils do not exhibit the

permanency of strength that often is responsible for the decision whether

128

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to use chemical stabilizers, the engineer should be aware of which soils

are frost susceptible and which are not. This Information Is given in

TM 5-330 (96) and summa'Tized below:

1. Non-frost susceptible soils

Inorganic soils containing less than 3 percent by weight of

grains finer than 0.02 mm.

Uniformly graded sandy soils having less than 10 percent by

weight of grains finer than 0.02 mm.

2. Frost susceptible soils

These soils are listed in Table 52 in general order of increasing

susceptibility. There is some overlapping of frost susceptibility

within the groups.

129

TABLE 52

FROST SUSCEPTIBLE SOILS WITH RELATION TO PAVEMENTS

Group Description

F-l Gravelly soils containing between 3 and 20 percent finer by weight than 0.02 mm are the least affected of the frost susceptible soils.

F-2 Sands containing between 3 and 15 percent by weight finer than 0.02 mm.

F-3 (1) Gravelly soils containing more than 20 percent finer than 0.02 mm by weight.

(2) Sands, except very fine sllty sands, containing more than 15 percent finer than 0.02 mm by weight.

(3) Clays with plasticity Indexes of more than 12. (4) Varved clays existing with uniform subgrade conditions,

F-4 (1) All silts Including sandy silts. (2) Very fine sllty sands containing more than 15 percent

finer than 0.02 mm by weight. (3) Clays with plasticity indexes of less than 12. (4) Varved clays existing with nonuniform subgrade

conditions.

NOTE: Groups are listed In general order of increasing susceptibility.


130

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SECTION VIII

CONSTRUCTION FACTORS

1. Introduction

The engineer, having evaluated the soil, selected the type and amount

of stabilizer, and considered the constraints Imposed by site weather con-

ditions, must survey the available construction equipment that might be

used to implement the stabilization work. The objective of the efforts

that transpire is to thoroughly mix the pulverized soil and the selected

stabilizing agent in the correct proportions with sufficient moisture to

permit proper and adequate compaction. A simple procedural approach that

might be followed consists of:

a. Initial preparation

1. shape the area to proper crown and grade

2. scarify, pulverize and prewet the soil as required

3. reshape to crown and grade

b. Processing

1. spread the selected stabilizer

2. add water as required

3. mix

4. compact

5. finish

6. cure as required

Types of scarifying, mixing and compaction equipment include a

131

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considerable range from that commonly used in agricultural operations to

highly efficient specially designed soil stabilization trains. Mixing

equipment may be grouped into traveling and stationary type roughly as

follows:

a. Traveling mixers

1. windrow type

2. flat type

3. multiple-pass rotary mixers

b. Stationary (or central) mixing plants

1. batch type

2. continuous flow type

Since the general objective of the operation and the principles in-

volved are quite similar, the engineer must make a decision considering

efficiency, expediency, and economy contingent upon the constraints

generally imposed by the situation at hand.

Some discussions concerning the limitations and operational details

of the various pieces of equipment used for mixing, placing and compacting

stabilized soil seems warranted and is presented in the following paragraphs.

2. Traveling Mixers

Construction steps for various types of traveling mixing plants are

discussed below:

a. Windrow type traveling plants

Since this type of stabilization equipment does not possess

sufficient power to pulverize most soils, preliminary pulverization

is usually necessary. The pulverized or prepared soil Is then bladed

into a windrow by a motor grader and formed by a screed to a uniform

132

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cross section. The stabilizer is applied to the top of the prepared

soil windrow with a suitable spreader. Mixing either occurs on the

underlying layer or in a traveling pugmill. In the latter case the soil

is picked up, fed to the pugmill and redeposited on the underlying layer.

Initial dry mixing takes place as the first few paddles pass through the

windrow. Water is then added through spray nozzles and the remaining

paddles complete the mixing. The mixed soil is deposited in a windrow,

spread by a grader and compacted.

b. Flat type traveling plants

Since most flat type mixing machines have a high speed pulverizing

rotor, preliminary pulverization is usually not necessary. The only

preparation required is shaping the soil to approximate crown and grade.

The stabilizer is spread over the soil with a suitable spreader. The

machine mixes the soil and stabilizer to a preselected depth on the

underlying layer. The first rotors in the machine pulverize and dry-mix

the soil and stabilizer. Water is measured through a meter and Injected

into the mixing chamber by a spray bar. The remaining rotors mix the

soil, water and stabilizer.

c. Multiple pass rotary mixers

Since most rotary mixers were not designed to scarify, initial

preparation includes loosening the soil with a scarifier, initial

pulverization, and shaping to approximate grade and crown. The

stabilizer is then spread on the ground and the first pass is made.

The objective at this stage is to distribute stabilizer throughout the

soil mass. Sufficient water is then added to bring the mixture to the

desired moisture content (this step may vary according to the stabilizer

used). The moisture is added in increments and each increment is olxed

133

with the soil and stabilizer. After the last increment of water is

added, mixing is continued until the soil, stabilizer and water are

thoroughly mixed through the entire depth and width of treatment. The

material is then ready for compaction and finishing.

d. Other types of traveling plants

Various construction equipment manufacturers have combined several

major pieces of equipment so as to eliminate one or more steps in the

stabilization process. One example of this combination Is the DUO-

STABILIZER manufactured by the Seaman Corporation. This piece of equip-

ment has the capability to scarify, pulverize, mix, level and compact

soil and stabilized mixes.

e. Classification by shaft orientation

Traveling plants can be further classified by the orientation of the

mixing shaft. Fugmill type plants have shafts that are parallel to the

direction of travel. The windrow type traveling plant previously

mentioned is an example of the parallel shaft machine. Due to the

orientation of rotation, it Is not feasible to attempt to pulverize or

reduce ln-place material with this type of machine. The parallel shaft

machines should therefore be used only for mixing preconditioned or

pulverized soil, water and stabilizer.

Traveling plants whose shafts lie across the direction of travel

are classified as transverse rotary mixers. These mixers may have the

capability of pulverizing ln-place material depending on rotor char-

acteristics such as speed, torque, depth of cut and production char-

acteristics of the plant as a whole. With pulverization capability the

plant has " one pass" potential. The flat type traveling plant and the

multiple-pass rotary mixers mentioned above are example of transverse

134

•

mixers. The flat type Is designed for single-pass operations while the

rotary mixer Is used for multiple-pass construction.

3, Related Stabilization Equipment

As soil stabilization outgrew Its "step-child" status, methods such

as manual distribution of dry admixtures gave way to specially designed

spreader boxes and bulk distributors that meter and produce a uniform flow

of agent. Spreaders are constructed along the same lines and possess similar

characteristics as the aggregate spreaders presently used In bituminous

surface treatment. The bulk spreaders or distributors range in capacity from

500 to 10,000 gallons. The Cyclone type bulk distributors are capable of

spreading a metered, uniform flow of dry admix (lime, cement, salt, calcium

chloride, etc.) on windrows of prepared soil or on ln-place material. Some

bulk distributors are equipped with pneumatic systems that pump the stabilizer

directly into the mixing chamber of a transverse rotary mixer or traveling

plant.

Emulsified asphalts and cutback asphalts are often spread by tank trucks

equipped with spray bars, although injection through the rotary mixer spray

bar system is more accurate and efficient. In the latter operation, the

mixer's spray system Is connected by a flexible hose line to a "nurse" truck

which supplies the liquid. These distributors contain reclrculatlon pumps

or internal paddles to keep the additives In solution.

4. Stationary (or Central) Mixing Plants

Under some conditions, the off-site stabilization of soils is more

suitable than on-slte or road mixing. Some advantages of plant mixing over

road mixing are:

135

a. On projects where submarglnal soils have to be used, the soil must

be processed to meet gradation requirements. It Is a relatively simple

matter for the contractor to Install a bin, feeder and pugmlll at the

plant to add the stabilizing agent.

b. A more uniform mix of the stabilizer, soil and water Is achieved.

c. No mixing is required on the road. This speeds up the on-slte

operations.

d. Moisture content may be more rigidly controlled.

e. Less loss of moisture occurs due to evaporation if travel time to

the laydown site is kept to a minimum and the soil is covered en route.

f. Rollers may be used directly behind the laydown operation.

g. One inspector at the plant can control the gradation, moisture

content, stabilizer content and mixing.

The combining of soil and stabilizer at a central plant is accomplished

by the use of batch or continuous type plants or by expedient type plants set

up at borrow pits.

The batch type plant operates on the same principles as the familiar

concrete or hot mix asphalt plants currently in use. Preselected amounts of

graded soil and stabilizer are combined with sufficient water to produce

optimum properties in a given batch. Batches are produced at Intervals of

30-90 seconds.

In the continuous type plant, addition of soil, stabilizer and water are

regulated to produce a continuous flow of mixture In preselected proportions.

Several manufacturers produce a placer-spreader-trimmer that Is of great

benefit in central plant mixed stabilization. This equipment receives the

mixed soil, places it on the roadway to the required depth, and trims the

136

surface to an Initial grade. As an expedient laydown method, slightly

modified asphalt pavers may be used to prepare the stabilized mixtures for

compaction and finishing. Vibrating pads mounted on the rear of asphalt

pavers have been used with some success for compaction. ■

5. Equipment Used for Expedient Soil Stabilization

a. On-slte stabilization

Equipment such as disc harrows, scarifiers, plows, motor graders,

and even large capacity scrapers have been utilized in the pulver-

ization and mixing of soils and stabilizing agents. With advances in

design of engineering equipment, these pieces of equipment have be-

come outdated from the standpoint of mixture uniformity. Economics

and timeliness In many Instances, however, will require that some

expedient method be used. In these situations equipment such as disc

harrows, plows, etc. are extremely useful provided close control is

I maintained on mixture uniformity.

b. Off-site stabilization

Expedient off-site stabilization operations have been set up using

on-slte stabilization equipment in a borrow pit. Experience has shown

that material produced in these operations is of doubtful quality due

to nonuniform mixing and extreme difficulty of controlling moisture.

This type of operation should be considered only as a last resort,

regardless of economic or timeliness considerations.

6. Equipment Requirements of Limitations for Particular Types of Stabilization

a. Lime stabilization

1. Subgrade or subbase

137

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A grader-scarifier and/or disc harrow can be used for Initial

scarification followed by a disc harrow or rotary mixer (flat type)

for pulverization. Self unloading tankers for dry application and

pressure liquid distributors are recommended for stabilizer

application for efficiency and assurance of uniform application.

The soil aggregate (or clod) size should be less than 2 Inches before

compaction. Ideally 100 percent of the soil clods should pass the

1-inch sieve and 60 percent should pass the No. 4 sieve.

Lime stabilization of heavy clays usually requires two mixing

stages. Initial mixing and blending should be followed by a day or

more of "mellowing." Final mixing can then take place resulting in

a more uniform product,

i. Subgrade

Although disc harrows and grader-scarifiers are suitable for

preliminary and initial mixing, high speed rotary mixers or

single pass travel plants are essential for final mixing. Motor

graders are generally unsuitable for mixing lime with heavy clays,

li. Subbase

Both blade and rotary mixing have been used successfully.

However, rotary mixers are preferred for more uniform mixing,

finer pulverization and faster operation. The National Lime

Association (86) offers methods for blade mixing. Rotary mixers

should make 1-3 passes depending on type of equipment and soil.

2. Base stabilization

Equipment requirements and limitations for base stabilization re-

semble those for subbases. However, a rooter, tractor ripper, or

preparator is usually necessary to reduce old asphalt surfaclngs to

138

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suitable size particles. Since only one mixing stage Is necessary,

a multiple pass rotary mixer can be used provided the base material

pulverizes readily. In other cases a single pass (pulverizing)

mixer should be used to Insure adequate pulverization.

3. Compaction

The most common practice for compaction Is to compact In one

lift, using a sheepsfoot roller until It walks out, followed by a

multiple wheel pneumatic roller (10 ton); a steel wheel roller Is

then used for finishing. Single lift compaction can also be accom-

plished using vibrating Impact rollers or heavy pneumatic rollers,

with light pneumatic or steel wheel rollers being used for finishing.

When light pneumatic rollers are used alone, compaction should be

accomplished In thin lifts less than 2 Inches thick. Slush rolling

of base courses with steel wheel rollers should be avoided as a

material of low shear strength Is produced at the surface.

4. Central plant mixes

Central plant mixes should be placed by a placer-spreader-

trlmmer or asphalt concrete laydown machine to maintain uniformity.

If these types of equipment are not available, aggregate spreaders,

tailgate dumping and grader spreading can be utilized. However,

spreading by use of a grader reduces the uniformity of the stabilized

mixture and Is not recommended,

b. Cement stabilization

1. RoadVeoostructlon

If the soil Is friable a windrow type traveling plant can be used

to mix the soil and cement. Thus, only scarification and blocking

139

into windrows Is needed for preparation.

Flat type or single-pass mixers require no preliminary preparation

unless the material Is extremely hard, such as an old roadway. In

these cases it would be beneficial to prewet and scarify.

With the multiple-pass mixer It Is necessary to scarify the soil.

Pulverization of the soil Is also necessary when clays or hard, dense

materials are encountered. These mixers are time consuming as several

passes are needed to thoroughly process the soil.

If stationary plant-mixed material Is used the mixture should be

spread with spreader boxes. Dumping In piles and spreading with

graders should be avoided as nonunlform densities often result.

Prior to compaction the soil-cement mixture should be pulverized

until 100 percent of the soil clods pass the 1-lnch sieve and 80

percent pass the No. 4 sieve.

2. Compaction

Plate vibrators, grid and segmental rollers have been satisfactorily

used to compact mixes of cement and nonplastlc granular soils.

Sheepsfoot rollers should be used for all but the most granular soils

with ballast Increased to provide contact pressure In the following

order: friable, sllty said clay-sand soils, 75 to 125 psl; clay-

sands, lean clays and silts that have low plasticity, 100-200 psl;

medium to heavy clays and gravelly soils, 150-300 psl. Lift

thickness for sheepsfoot rollers should not exceed 8 Inches (loose).

Pneumatic tired equipment can be used to compact very sandy soils

with little or no binder. A heavy roller Is used to compact and a

light roller Is used to finish. Coheslonless sand may be compacted

with large track type tractors with screed plates. Compaction Is

140

, . ■•

obtained by the weight and vibration of the tractor. Twelve-ton,

three-wheeled steel rollers are commonly used In some areas to

compact granular soils. Soils containing little or no binder

material and that have low plasticity are best suited for this

method. Maximum lifts should not exceed 6 Inches,

c. Asphalt stabilization

Since stabilization with bituminous materials requires a well

mixed and uniform product, central plant mixing is preferred. If in-

place mixing is required, a traveling plant mixer should be used.

Those pieces of equipment which pick the soil up from the subgrade and

mix in a pugmill are preferred. Grader mixing of soil and liquid

should not be used due to poor mixing and the resulting nonunlform

product.

The asphalt should be distributed to the soil mass through the spray

bar system in the mixing chamber. Use of truck distribution of

asphaltlc materials causes puddles in the wheel tracks and a resulting

nonunlform mixture.

Compaction with a combination of pneumatic tired and steel wheel

rollers yields the highest density.

7. Summary of Construction Requirements and Limitations

a. Lime stabilization

Pulverization and mixing should continue until the lime is

uniformly mixed and the soil clod size is such that 100 percent passes a

1-inch sieve and 60 percent passes the No. 4 sieve (exclusive of any

gravel and stone).

b. Cement stabilization

141

Pulverization and mixing should continue until the cement Is

uniformly mixed and the soil clod size Is such that 100 percent

passes a 1-inch sieve and 80 percent passes the No. 4 sieve

(exclusive of any gravel or stone).

c. Bituminous stabilization

Central batch plants, together with other specialized equipment,

are necessary to produce a uniform, high quality bituminous

stabilized soil.

As discussed in this section, various types of scarifying, pul-

verizing, mixing, spreading and compacting equipment can be used for

a particular stabilization job. The type of equipment selected by

the engineer Is often determined by availability. Thus, specific types

of equipment have not been recommended, but instead general guidelines

suggested.

Information contained in this chapter has been used in forming

Tables 14, 15 and 16 presented previously.

142

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SECTION IX

ENVIRONMENTAL FACTORS

1. Introduction

Stabilization - particularly with chemicals - may be ineffective unless

the weather and rainfall conditions are satisfactory. It is the intent of

this section to discuss the situations which may be detrimental to stabilized

soils and to describe general methods which can warn the engineer of these

conditions. Some of these are expressed in terms of constraints or pre-

cautions which will prohibit the application and use of certain stabilizers.

It is realized that military engineers faced with hasty forward construction

may not always be able to honor these constraints and will have to accept a

substandard job. However, they can still be of value in planning a program,

and in aiding In the selection of a particular stabilizer when more than one

type will suffice.

2. Sources and Types of Available Environmental Information

A review of literature reveals that little information has been developed

to quantitatively define environmental factors. Welnert (97) has reported on

a climatic index which was developed to indicate where moist environments

might be harmful to certain unstablllzed aggregates. The Corps of Engineers

use a freezing index (96) to determine depths to which frost might penetrate

pavements. Both of these - and similar concepts developed by others - are

helpful in pavement design, but appear to be of limited value in defining

environmental factors which must be considered with stabilized soils, partic-

ularly during the construction period.

143

Until appropriate factors are quantified, the engineer must be satisfied

with a more qualitative approach which uses general environmental Information

In conjunction with certain Information presented later In this section.

Considerable engineering judgment must be exercised, but an awareness of the

possible problems may prevent unsatisfactory jobs.

In general, sufficient environmental Information should be obtained to

develop a general climatic profile of the area In which construction Is being

planned. Most of the necessary Information can be obtained from Air Force

meteorologists. Otherwise, local weather records, records available from

ESSA (Environmental Science Services Administration) and other such sources,

can be used.

The following information can be helpful:

a. Temperature

1. Average maximum and minimum monthly temperatures

2. Date of last freeze In spring and first freeze In fall

(earliest dates, latest dates and average dates are helpful)

3. Freezing Index (number of degree days of temperature below 32eF)

4. Ground temperature versus air temperature relationships

b. Rainfall

1. Average annual rainfall

2. Average monthly rainfall

3. Average minimum and maximum monthly rainfall

3. Influence of Temperature and Rainfall on Soil Stabilization

a. Temperature

Two primary factors must be considered with respsct to temperature

influence on chemically stabilized soils. First, the temperature must

144

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be sufficiently high to permit mixing of stabilizer and soil, and for

necessary chemical reactions to occur. Second, stabilized materials

which require curing must have adequate curing time to resist the effects

of subsequent freezing temperatures or freeze-thaw cycles. In both re-

spects, requirements for bituminous materials differ from cement and lime.

Bituminous stabilization requires high enough temperatures to obtain

thorough mixing, and to subsequently evaporate the volatlles (either hydro-

carbons or water), as well as temperatures which permit adequate compaction.

Llme-and cement-stabilized soils are dependent on chemical reactions for

strength gains. At temperatures near or below freezing these reactions

virtually halt, but as the temperatures rise, the speed of reaction roughly

doubles for every 10oC Increase In temperature. Thus, llme-and cement-

stablllzatlon must take place under favorable temperatures to obtain

effective strength Increases; however, temperature effects on lime are

more critical than for cement. Soils can be modified with lime and cement

with little regard for temperature unless It Is well below freezing and

expected to remain that way for a lengthy period of time.

General requirements for stabilized soils with respect to temperature

are discussed in greater detail below:


1. Asphalt cement

In most cases where asphalt cement is used, it will be hot-

mixed in central plant, transported to location and placed.

Various temperature specifications exist for this material (13),

but all generally require that material shall not be placed unless

the air temperature is at least 40*F and rising, and that place-

ment be discontinued when the air temperature reaches 40oF and

U5

Is falling. In addition, the material should not be placed

on a frozen underlying layer. The above applies particularly

for thin layers; for thick lifts the temperature Is usually not

as Important since the heat Is held In the material for longer

periods of time.

11. Cutback asphalts

The Asphalt Institute (16) has suggested temperatures

(Table 53 and Figure 29) to ensure that the asphalts will not be

too viscous to spray and mix with the aggregate. It Is also

suggested that the aggregate temperatures be not less than 50eF.

In expedient construction, It Is felt that this requirement can

be relaxed to a minimum aggregate temperature of 40oF If correct

spraying temperatures can be maintained. Since these asphaltlc

materials contain hydrocarbon volatlles, low temperatures will

somewhat decrease the speed of evaporation. Mixing time may need

to be increased as temperatures decrease.

111. Asphalt emulsions

Temperature ranges for mixing and spraying of emulsions are

also given In Table 53. It Is felt that the low temperature

restrictions can again be relaxed to 40oF, and In extreme

emergencies, somewhat lower mixing temperatures can be tolerated.

However, since the volatile component Is water, temperatures at

or below freezing will not allow volatlles to escape. In

addition, freezing temperatures can be harmful to emulsions even

before they are applied to soils.

2. Lime-and cement-stabilization

As mentioned previously, these materials rely on chemical reac-

146

TABLE 53

MIXING AND SPRAYING TEMPERATURES FOR

VARIOUS GRADES OF LIQUID ASPHALT

Suggested Temperature Type and Grade

For Mixing* For Spraying

RC, MC ( and SC Grades

! 30 60-105oF 1 70 95-140oF See

250 135-1750F Figure ! 800 165-205oF 29 | 3000 200-240oF

Anlonlc

RS-1 ** 75-130oF RS-2 ** 110-160oF MS-2 50-140oF 100-1608F SS-1 50-140oF 75-130oF j SS-lh 50-140oF 75-1308F

Catlonlc

RS-2K ** 75-130oF RS-3K ** 110-160oF CM-K 50-1400F 100-160oF SM-K 50-140oF 100-160oF SS-K 50-140oF 75-130oF SS-Kh 50-140oF 75-130oF

♦Because the aggregate temperature controls the mix temperature, aggregate temperatures below 50oF or above the temperature of the liquid asphalt should not be permitted.

**Seldom used for mixing.

[after Asphalt Institute (16)]

147

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tlons for strength Increases. In general, cement-stabilized soils

can be expected to gain strength at a more rapid rate than lime-

stabilized soils. The Portland Cement Association recommends that

soil-cement not be placed when the temperature Is 40"F or below.

It is also Important that the stabilized material not be subjected

to freezing conditions during the period of strength gain, as this

may disrupt the material due to frost action. For this reason,

soil-cement should not be subjected to freezing temperatures for a

period of 7 days after placement. If short, infrequent freezes are

anticipated, an Insulating covering of hay, straw, etc. may be used

during the curing period.

Lime-stabilized soils require about 4 weeks of 60-70oF temper-

ature to allow hydratlon (86)• The stabilized soils should not be

subjected to freezing temperatures during the hydration period.

Lower temperatures, as long as they are above freezing will only

retard strength gain.

There are no well-documented requirements for modified soils.

However, the necessary chemical reactions (cation exchange, etc.)

will take place fairly rapidly as long as the temperatures do not

drop below freezing. If freezing does occur, the chemical processes

should reactivate as the temperatures increase, and modification will

be delayed. In general, whenever temperature conditions for sta-

bilization cannot be met, modification can still be expected. But

it is necessary that adequate mixing of stabilizer and soil be

accomplished before low temperatures set In.

b. Rainfall

Wet weather will not always terminate a stabilization project. If the

149

stabilization operation is properly planned, then only certain portions

will be halted by rainfall. This is discussed below.

■


Mixing of bitumen on the roadway cannot be accomplished

effectively during periods of rainfall. Heavy rains on mixed but

uncompacted stabilized material may result in nonuniform bitumen

coating. Central plant mixing can take place during rainfall» ■

but placing and compaction of the hot-mixed asphalt concrete should

not be attempted until the rain ceases. Rainfall after compaction

can be detrimental if cutback or emulsified asphalts are used as It

may prevent adequate evaporation of the volatlles. Extended

periods of rainfall after compaction may prevent the remaining

volatlles from evaporating and result in an unstable layer.


Lime should not be spread during periods of rainfall as uniform

distribution in the soil mass will not be possible during mixing.

Rainfall during mixing and compaction can be tolerated provided the

moisture content build-up In the soil does not exceed that required

for compaction. Light rains curing the curing period can be help-

ful; however, heavy rainfall may cause erosion of the stabilized

layer.


Cement should not be spread during periods of rainfall as

uniform distribution in the soil mass will not be possible during

mixing. If rains do occur during spreading every attempt should

be made to mix the cement into the soil before the cement starts

hydrating. Rainfall during mixing and compaction can be tolerated

150

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provided the moisture content does not exceed that required for

compaction. Light rains during the curing period can be helpful;

however, heavy rainfall during early periods of the curing can

create erosion of the stabilized layer.

4. Summary of Environmental Requirements and Limitations

Yearly temperature and rainfall data are available for most parts of

the world and should be collected during construction planning stages. If

at all possible, stabilization should be scheduled during periods of high

temperature and low rainfall.

Specifically, the engineer should make every attempt to schedule

construction such that:

a. spreading of the stabilizer, mixing and compaction occurs during

periods of warm, dry weather

b. curing occurs during warm and relatively dry weather in order

that sufficient strength is achieved prior to traffic or prior to

freeze-thaw cycles

Information contained in this section was used in developing Tables 14,

15 and 16 presented previously.

151

SECTION X

RECOMMENDATIONS FOR FUTURE RESEARCH

1. Introduction

Should the need arise, the Air Force must be In a position to provide

facilities to support aircraft operations throughout the world. Thus

pavements, as well as other support facilities, must be provided for both

aircraft and supply operations. The construction of these pavements often

requires the use of stabilized materials for either the subgrade or base

course. With this In mind, the Air Force has embarked on a program of re-

search to provide engineers with the necessary knowledge to effectively

utilize stabilized materials as an integral part of the pavement.

A research project undertaken by Texas A&M University has resulted in

the soil stabilization index system described in this report. The index

system presents Information for the engineer so that he can systematically

determine:

a. the type of stabilization that can be used with a particular soil

b. the quantity of stabilizer to be used

c. a strength indication, which may or may not be compatible with a

pavement desigr system

However, this system assumes that stabilization Is necessary, and further-

more it assumes that the layer in the pavement structure that will be

stabilized has been ascertained. To properly determine the need for

stabilization and the location of the stabilized layer in the pavement

structure, pavement design methods must be utilized.

152

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Criteria that were used to develop the soil stabilization Index system

were based on the experience and research of many Individuals and groups.

Unfortunately the majority of stabilized materials have been used In highway

systems rather than airfield pavements, and furthermore the majority of

reported stabilization research has been on North American soils. Thus, the

criteria are based on only a limited number of soils when one considers the

worldwide application of the system by the Air Force, and on pavement systems

which are loaded with vehicles of lower gross loads, lower tire pressures and

Aimpler wheel configurations than might be needed by the Air Force.

It is Important that these and other limitations of the developed soil

stabilization index system be recognized and that the Air Force carefully

plan future research In areas of soil stabilization where gaps in knowledge

exist. In this manner, unnecessary duplication will not exist. It is the

Intent of the authors to indicate the gaps in knowledge as revealed by the

development, of the index system, and furthermore to suggest future research

needs that should be undertaken by the Air Force so stabilized materials can

be effectively used as an Integral part of the pavement. Below, several

general areas of recommended research are discussed followed by research

requirements and tests needed to complete Phase II of the research on the

index system.

2. General Areas of Recommended Research

In some Instances the research discussed below overlaps and extends

the scope of research needed to validate the index system.

a. A systems approach is needed to determine and to Illustrate the

inter-relationship of pavement design and soil stabilization.

The systems approach views the entire system of components as an

153

entity rather than simply as an assembly of individual parts. Each

component or variable in the system is designed to fit properly with the

other components of the system rather than functioning by Itself. The

system can be divided into subsystems for the purpose of defining

research needs, thus allowing both the sponsor and the research agency

to more clearly define the mission of the particular research project In

light of the overall research needs of a broad general program such as

pavement design. The systems approach (98, 99, 100, 101, 102, 103) also

inserts compatibility, interaction and feedback between pavement design

methods, material characterization and field performance.

More specifically, the systems approach points out the need for

material characterization to provide a basis for analyses to preclude

failure of the pavement structure due to rupture, distortion and dis-

integration. In addition, the interaction of traffic, construction

variables and environmental conditions must be considered when char-

acterizing stabilized materials for both short- and long-term use.

The Importance of field evaluation and feedback to the design method

can not be overemphasized and considerable effort should be expended

on collecting data on existing and planned facilities.

An example of a simplified systems approach with emphasis on

stabilized materials is illustrated in Figure 30.

b. A pavement design method should be developed which will adequately

recognize the benefits of utilizing stabilized materials in various

layers of the pavement.

A pavement design method should be capable of identifying the

optimum location and thickness of stabilized layers in the pavement

for specific aircraft and for a range of subgrade strengths. It

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should fully utilize the strength available from the stabilized mate-

rial. This Is not always the case with the present CBR design proce-

dure. For example, cement-stabilized materials are now restricted to

a maximum design CBR of 50. This value was reportedly based on per-

formance of test sections constructed during World War II. Its pur-

pose was to reduce reflected shrinkage cracks and to Insure an ade-

quate thickness of overlying material to prevent the wearing surface

from slipping at the interface with the stabilized base. With the pres-

ent tendency towards thicker cross sections, this requirement may be

completely outdated, or at least Invalid for the majority of stabili-

zation projects.

A rational test method should be included which will adequately

consider the benefits of stabilized materials. This test method should

result in parameters which are compatible with the pavement design

method. Such a pavement design system and method for determining

material properties has been proposed by Monismith (102).

c. The soil stabilization index system as a whole should be validated

with soils and airfield construction experience from throughout the world.

This should be a continuing operation and criteria that are shown

to be invalid should be corrected. Undoubtedly, much of the Information

that is needed will become available from other than U. S. military

sources. However, the Air Force itself can collect much of this in-

formation as discussed in the recommendation below.

d. The Air Force should institute a debriefing system for its officers

who have received field experience in soil stabilization.

The personnel rotation system used by the Armed Forces does not lend

itself to continuity of knowledge from previous construction projects.

In Viet Nam, for example, excellent knowledge is available from officers

156

who have conducted soil stabilization projects In that country. But when

these personnel are reassigned they take this Information with them

leaving techniques and methods to be rediscovered by the next man on the

Job. It cannot he emphasized too strongly that the Air Force should

take steps to prevent this excellent first-hand information from being

lost. By means of a controlled debriefing session, the Air Force could

obtain, sort and disseminate this Information. This would not only

provide solutions to many existing problems, It would also help to

Identify problem areas that must be researched.

The "key word In context" method (104) would provide a systematic

means of retrieving and storing this Information. Key words, which

relate to all Important aspects of any particular stabilization method,

serve to "Jog" one's memory, and this Information - Including numerical

data - can be stored and arranged for recall with a digital computer.

e. Air Force requirements for expedient and nonexpedlent construction

should be carefully detailed.

These requirements are extremely Important as they will Influence

both the stabilization Index system and any subsequent pavement design

system which might be developed.

f. Detailed durability requirements and appropriate durability tests

for lime, cement and asphalt stabilized materials are sorely needed.

Present durability requirements have been developed primarily for

highway pavements, and It Is not known whether these are applicable to

airfield pavements. Thus, detailed durability requirements should be

defined for airfield construction, and durability tests should be

adopted or developed to Insure that these requirements are met.

157

„wvuewmtif?:?''

From the testing viewpoint, only the freeze-thaw test used for

cement stabilized soils is a well-accepted durability test, and it is

not apparent that this is an appropriate durability test to use on a

worldwide basis. Attempts to correlate unconfined compression tests

with durability (such as has been done by the Portland Cement Association

and the University of Illinois) are notable improvements in durability

testing, at least from the standpoint of simplifying and decreasing the

amount of time for durability tests. More detailed investigation of the

validity of these tests appears to be warranted.

It should be emphasized that because of the varying requirements of

the Air Force, which range from mobility to long-term airfields, dur-

ability specifications for stabilized materials under varying situations

becomes a significant problem,

g. Field methods of mixing stabilizers into soils should be investigated.

The problems in this area are considered to be:

1. determining those soil and stabilizer properties that influence

mixing

2. determining the degree of mixing that is required

3. determining the best type of mixing equipment

The Air Force Weapons Laboratory is presently reviewing this problem,

and several comments in this respect are discussed below.

First, the problem of mixing Is a very practical one, and one should

be wary of highly theoretical approaches to the problem. Detailed in-

vestigations of physico-chemical properties of soils that influence

mixing can be performed without ever solving the real problem of how to

distribute the stabilizer into the soil.

158

..:■, .-. - tm OK •— ■» -■'■

Second, It Is believed that more than soil properties alone In-

fluence mixing. Rather, It Is the compatibility of soil and stabilizer

that must be Investigated. Thus, If one Is looking at physico-chemical

properties of soils without looking at the Influence of the stabilizer

on these properties, the result Is liable to be misleading.

Third, the basic need seems to be a fresh approach to the mixing

equipment, which has, for the most part, remained unchanged In concept

since World War 11. In cohesive soils, for example, the processes of

plowing, discing and tilling are holdovers from farming operations. At

best, their efficiency is low. Alternate approaches to destroying the

natural cohesion of the clods of soil are by adding sufficient liquid,

by vibration, by forcing the clods between narrowly spaced rollers,

etc. Once these clods are broken down, the stabilizer can be easily

added to the soil. Another example is a new method of producing hot-

mix asphalt stabilized materials which Is presently used In the state

of Washington whereby the asphaltlc cement is sprayed directly into

the rotating dryer Instead of being mixed in a separate pugmlll. This

method can be used in relatively poor environmental conditions, the

equipment is portable, it can be used for expedient as well as nonex-

pedlent operations, and it will provide a stabilized material with

immediate strength and durability.

Finally, it is necessary to determine what soil properties need to

be improved as this may dictate the amount of mixing necessary. If

strength improvement Is the sole criterion, it may be done at the

expense of durability. The Air Force requirements vary and durability

is not particularly a problem in short term mobilir.y operations whereas

shear strength is. In nonexpedient operations, durability may be more

159

. .■ ■

Important than short term strength gains.

h. The feasibility of calcining soils rather than stabilizing In the

conventional manner should be Investigated.

Many soils can be effectively converted to synthetic aggregates

by kiln-firing. Instead of using temperatures high enough to produce

"bloating" (resulting in lightweight aggregates), the Texas Highway

Department has used lower temperatures to produce a durable but non-

expanded aggregate. In several instances this material has been mixed

with a local field sand to produce a satisfactory base course. It has

also been used in asphaltlc concrete and surface treatments. Although

lightweight aggregates have been used for over 30 years and have a

proven performance record, aggregates produced with lower temperatures

have been used less than 10 years and thus have a shorter experience

record. It is believed that the economics and logistics of such an

operation should be Investigated Initially, followed by detailed dur-

ability and strength testing of aggregates produced from a variety of

soil types.

1. A long range program to develop new chemical additives should be

instigated.

Although past research on the development of additives other than

lime, cement and bitumens has not been too encouraging, It is felt that

research In this area should not be terminated. Rapid advances In the

chemical field have produced new compounds dally and eventually this

must result in improved stabilizers which are also economically fea-

sible. Desirable characteristics of such stabilizers are:

1. produce high failure strains under slow rates of loading

2. produce high elastic moduli at fast rates of loading

160

3. adhere to soils coated with water or make use of the water

that coats soil grains to produce an Increase In strength

j. Environmental and construction factors In the Index system should

be quantified.

Climate and construction factors now enter the Index system

primarily as precautions, that is, they serve to warn the engineer that

he must have certain climatic conditions and equipment to perform a

particular stabilization effort. To be of greatest aid to the engineer,

environmental and construction factors should be quantified. If this

can be accomplished, this aspect of the index system will be greatly

simplified. There is no doubt that these two important factors can be

improved upon during the course of Phase II research on the index sys-

tem, but it is also obvious that the development of a mathematical

model cannot be accomplished within the scope of the present research.

3. Specific Research Recommendations Related to Validation of the Index System

Review of criteria and development of the soil stabilization index system

has revealed certain specific areas of research that should be undertaken.

In each instance, some degree of research will be accomplished during the

validation of the Index system. However, such a significant amount of in-

formation is required, and the scope Is so broad, that it is believed that

additional long range research will be necessary to complete the validation.

Specific tests and criteria that need to be evaluated follow:

a. Marshall stability test criteria for asphalt stabilized soils should

be reevaluated.

The criteria used in the index system for asphalt treated materials

were based on the Marshall test method. These criteria are probably

161

iiimwm—iiWMW I ■■•

overly conservative for asphalt cement treated base, but they may not be

conservative for emulsion-and cutback-stabilized matetlals used for

airfield pavements. The selected criteria need to be carefully reviewed,

and new tests should be specified If the Marshall test proves to be

unsatisfactory.

b. Verification of the pH test used for estimating lime contents

should be undertaken on soils of world-wide distribution.

This test, because of Its simplicity, offers considerable promise

In rapidly estimating lime contents and In determining the reactivity of

lime with soils. The University of Illinois, and others, have information

on this test method, but It Is presently limited to only a small number

of soil types. Even though additional Information will become available

during verification of the Index system, this will still encompass only

a small number of the many worldwide soil types. Thus, even If the test

proves to be satisfactory for the soils Investigated, continual verifi-

cation will still be needed.

c. The criteria used for the cement stabilization subsystems should be

closely reviewed.

The cement stabilization subsystems are based on criteria largely

obtained from the Portland Cement Association. A wider distribution of

soils should be Investigated using the Portland Cement Association tests.

Also, the pH and sulfate tests should be validated on a wider range of

soils.

4. Proposed Program for Phase II Research

Phase II research associated with the development of the soil stabilization

Index system will be aimed at the following specific objectives:

162

tumUW-Hurtstumm

a. Laboratory verification of the Index system will be undertaken.

Soils with the properties listed below will be tested to determine

Initial physical properties and will then be stabilized with the

appropriate stabilizers according to the Index system. The selection of

soil properties was governed by the need to test each major group In the

Index system with particular emphasis on a few groups where the present

criteria are most questionable. An attempt will be made to locate as

many as possible of these soils from existing or proposed Air Force

facilities so that field performance Information can be obtained.

Sample No. Percent Passing

No. 200 Sieve

Plasticity Index

Sulfate Content

Organic Content

1 >25 >30 high low

2 >25 >30 low low

3 >25 >30 high high

4 >25 >30 low high

5 >25 >10<30 high low

6 >25 >10<30 low low

7 >25 >10<30 high high

8 >25 >10<30 low high

9 <25 <6 low high

10 <25 <6 low low

11 <25 Non-plastic low low

12 <25 >10 low low

13 <25 <10 low low

14 >25 <10 low low

The following standard tests will be peformed on each soil:

1. grain size analysis

163

./.•■■•

2. Atterberg limits

3. moisture-density relations

4. pH

5. sulfate content

6. organic content

Each soil will then be stabilized with the most appropriate stablllzerCs).

In most cases two and perhaps three stabilizing agents will be used. For

each stabilizing agent, the following tests are anticipated:

1. Lime

At least three lime contents will be selected to bracket the

optimum lime content. At each lime content,moisture-density and pH

tests will be performed. Unconfined compression tests will be

performed on freeze-thaw specimens (at three different cycles of

freezing and thawing), on soaked specimens and on unsoaked specimens,

all molded at the optimum moisture content for each lime content.

2. Cement

At least three cement contents will be selected to bracket the

optimum cement content. At each cement content, moisture-density

tests will be performed. Specimens will be molded at the optimum

moisture content for each cement content and will be subjected to

appropriate wul-dry and freeze-thaw cycles. Unconfined compression

tests will be performed on specimens, and the validity of the rapid

tests for determining cement content will be ascertained.

3. Asphalt

It is anticipated that roughly four of the selected soils will

be suitable for stabilizing with asphalt cement. The remainder will

be stabilized with cutbacks and emulsions. A "fluids"-density curve

164

:

will be obtained on each stabilizer-soil combination. Marshall

stability tests will be performed on specimens at two different

temperatures (140° and 770F) and Moisture Vapor Susceptibility

tests will also be conducted.

b. Selected soils used to verify the index system will be subjected to

repetitive load testing.

The purpose of this testing is to determine the elastic modulus and

fatigue behavior of stabilized soils. Exploratory testing on a limited

number of soil types will be performed to develop the most acceptable

test procedure and equipment. The procedures initially used will be:

1. Unsupported beam

2. Unsupported diaphragm

3. Supported diaphragm

The most suitable of these procedures will then be used to test other

stabilized soils. Based on information obtained from these tests, an

attempt will be made to predict certain elastic parameters from the more

standard tests performed on stabilized materials. Not only will the

repeated load tests provide validation for the index system, it is

hoped that this information will form the genesis for combining a pave-

ment design system with the soil stabilization index system.

c. The index system in its present form will be presented and discussed

with various authorities in soil stabilization.

The index system presented In this report resulted from considerable

literature survey and discussion with many individuals who have not seen

the final result of the system. Before the system is subjected to a

significant amount of laboratory verification, it is believed that these

Individuals - many of whom represent producer organizations - should be

165

given the opportunity to critique the system and make their suggestions

regarding possible areas of revision. This will be done only with prior

Air Force approval.

166

APPENDIX A

EXPEDIENT SUBGBADE STABILIZATION SYSTEM

167

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170

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pH OF 12.4

DETERMINE

pH

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MIXTURE

AFTE

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APPENDIX J

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CONTENT

FROM

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55

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171

Temperature of Aggregate. "F

RC 140

Type of Cutback

MC

115

100

90

65

40 —^^^—

Grade of Cutback

SC Old New T KM

1500

800

250

70

0 10 12.5 25


Example: For aggregate temperature of 100oF and 10% passing #200 sieve, use MC 800 cutback.



172

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0o/c SILICA CONTENT

////// APPROXIMATE

EFFECTIVE RANGE OF CATIONIC EMULSION

APPROXIMATE \ ^EFFECTIVE RANGEN

OFANIONiC EMULSIONS

100% ALKALINE OR ALKALINE EARTH OXIDE CONTENT

100%

FIGURE 37. Approximate effective range of cationic and anlonic emulsions on various types of aggregates


174

.

TABLE 54


FOR BITUMINOUS STABILIZATION IN EXPEDIENT SUBGRADES


Environmental

Construction

When asphalt cements are used for bituminous stabilization, proper compaction must be obtained. If thin lifts of asphalt concrete are being placed, the air temperature should be 40oF and rising, and compaction equipment should be used immediately after lay down operation. Adequate compaction can be obtained at freezing temperatures if thick lifts are utilized. When cutbacks and emulsions are utilized, the air temperature and soil temperature should be above freezing. Bituminous materials should completely coat the soil particles before rainfall stops construction.

Central batch plants together with other specialized equipment, are necessary for bituminous stabilization with asphalt cements. Hot dry weather is preferred for all types of bituminous stabilization.

175

TABLE 55


FOR CEMENT STABILIZATION IN EXPEDIENT SUBGRADES


Environmental

Construction

If the soil temperature is less than 40oF and is not expected to increase for one month, chemical reactions will not occur rapidly, and strength gain of the cement- soil mixture will be minimal. If these environmental conditions are expected the cement may act as a modifier.

If heavy vehicles are allowed on the cement stabilized soils prior to a 10 to 14 day curing period, certain pavement damage can be expected. Construction during periods of heavy rainfall should be avoided. Compaction of cement stabilized soil should be completed within 5 to 6 hours after spreading and mixing.

176

" ■- ■. ■ s ■■ ' -.■ .

TABLE 56


FOR LIME STABILIZATION IN EXPEDIENT SUBGRADES


Environmental If the soil temperature is less than 40*F and Is not expected to increase for one month, chemical reactions will not occur rapidly, and the strength gain of the lime-soil mixture will be minimal. If these environmental conditions are expected the lime may act as a soil modifier.

Construction No construction precautions necessary.

177

TABLE 57



Crushed Stones and | Sand Bitumen Soil Bitumen Sand-Gravel Bitumen |

Hot Mix: Hot Mix: i Asphalt Cements Asphalt Cements 1

60-70 hot climate 40-50 hot climate I 85-100 60-70 j 120-150 cold climate 85-100 cold climate

Cold Mix: Cold Mix: Cold Mix: ! Cutbacks Cutbacks Cutbacks i See Figure 35 See Figure 35 See Figure 35

| Emulsions Emulsions Emulsions See Table 60 See Table 60 See Table 60 1 See Figures See Figures See Figures |

! 36 and 37 to 36 and 37 to 36 and 37 to | determine if determine if determine if

a catonlc or a catonic or a catonic or anonic emulsion anonic emulsion anonic emulsion

| should be used should be used should be used

178

TABLE 58



Lbs. of emulsified asphalt per 100 lbs. of dry aggregate when percent passing No. 10 sieve Is:

50* 60 70 80 90 100

0 6.0 6.3 6.5 6.7

2 6.3 6.5 6.7 7.0

4 6.5 6.7 7.0 7.2

6 6.7 7.0 7.2 7.5

8 7.0 7.2 7.5 7.7

10 7.2 7.5 7.7 7.9

12 7.5 7.7 7.9 8.2

14 7.2 7.5 7.7 7.9

16 7.0 7.2 7.5 7.7

18 6.7 7.0 7.2 7.5

20 6.5 6.7 7.0 7.2

22 6.3 6.5 6.7 7.0

24 6.0 6.3 6.5 6.7

25 6.2 6.4 6.6 6.9

*50 or less.


7.0

7.2

7.5

7.7

7.2

7.5

7.7

7.9

7.9 8.2

8.2 8.4

8.4 8.6

8.2 8.4

7.9 8.2

7.7 7.9

7.5 7.7

7.2 7.5

7.0 7.2

7.1 7.3

179

TABLE 59


p = 0.02 (a) + 0.07 (b) + 0.15 (c) + 0.20 (d)

where: p = percent of residual asphalt by weight of dry aggregate,

a " percent of mineral aggregate retained on No. 50 sieve.


c = percent of mineral aggregate passing No. 100 and retained on No. 200 sieve.

d • percent of mineral aggregate passing No. 200 sieve.

TABLE 60


t. *

Percent .(* Passing

if 200 Sieve

Relative Water Content of Soil ■i

Wet (5%+) Dry (0-5%)


5-15 SS-1, SS-lh (or SS-K, SS-Kh) SM-K (or SS-lh*, SS-1*)


*Soll should be pre-wetted with water before using these types of emulsified asphalts.


180

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181

TABLE 62

APPROXIMATE LIME CONTENTS

Soil Type

Approximate I percent bv s

:reatment,

Hydrated Lime Quicklime

Clayey gravels (GC, GM-GC) (A-2-6, A-2-7) 2-4 2-3

Silty clays (CL) (A-6, A-7-6) 5-10 3-8

Clays (CH) (A-6, A-7-6) 3-8 3-6


182

APPENDIX B

EXPEDIENT BASE COURSE STABILIZATION SYSTEM

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Type of Cutback

MC

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100

90

65

40

SC

Grade of Cutback Old 5

New 3000

4 1500

3 800

250

70 0 10 12.5 25


Example: For aggregate temperature of 1000F and 10% passing #200 sieve, use MC 800 cutback.



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0% SILICA CONTENT

////// APPROXIMATE


APPROXIMATE \'EFFECTIVE RANGEx

OFANIONiC EMULSIONS

100°/. ALKALINE OR ALKALINE EARTH OXIDE CONTENT

l000/c

FIGURE 44. Approximate effective range of catlonic and anlonlc emulsions on various types of aggregates


190

■

TABLE 63


FOR BITUMINOUS STABILIZATION IN EXPEDIENT BASE COURSES


Environmental

Construction

When asphalt cements are used for bituminous stabilization, proper compaction must be obtained. If thin lifts of asphalt concrete are being placed, the air temperature should be 40oF and rising, and compaction equipment should be used Immediately after lay down operation. Adequate compaction can be obtained at freezing temperatures If thick lifts are utilized. When cutbacks and emulsions are utilized, the air temperature and soil temperature should be above freezing. Bituminous materials should completely coat the soil particles before rainfall stops construction.

Central batch plants together with other specialized equipment, are necessary for bituminous stabilization with asphalt cements. Hot dry weather Is preferred for all types of bituminous stabilization.

191

I . ■ '

TABLE 64

ENVIRONMENT AI. AND CONSTRUCTION PRECAUTIONS

FOR CEMENT STABILIZATION IN EXPEDIENT BASE COURSES


Environmental If the soil temperature is less than 60 to 70oF and is not expected to increase for one month, chemical reactions will not occur rapidly, and strength gain of the cement- soil mixture will be minimal. If these environmental conditions are expected, an alternative stabilizer should be investigated for possible use.

Construction If heavy vehicles are allowed on the cement stabilized soils prior to a 10 to 14 day curing period, certain pavement damage can be expected.

192

■ ■■ ■ ■ • m ■ . ■ •

TABLE 65


FOR LIME STABILIZATION IN EXPEDIENT BASE COURSES


Environmental If the soil temperature is less than 60 to 70oF and is not expected to Increase for one month, chemical reactions will not occur rapidly, and the strength gain of the lime-soil mixture will be minimal. If these environmental conditions are expected an alternative stabilizer should be investigated for possible use.

Construction If heavy vehicles are allowed on the lime stabilized soils prior to a 10 to 14 day curing period, certain pavement damage can be expected.

193

TABLE 66



Crushed Stones and i Sand Bitumen Soil Bitumen Sand-Gravel Bitumen |

Hot Mix: Hot Mix: 1 Asphalt Cements Asphalt Cements | j 60-70 hot climate 40-50 hot climate \ i 85-100 60-70 j | 120-150 cold climate 85-100 cold climate

Cold Mix: Cold Mix: Cold Mix: 1 Cutbacks Cutbacks Cutbacks | See Figure 42 See Figure 42 See Figure 42 1

Emulsions Emulsions Emulsions i See Table 71 See Table 71 See Table 71 I See Figures See Figures See Figures 1 43 and 44 to 43 and 44 to 43 and 44 to

determine if determine if determine If a catonic or a catonic or a catonic or

| anonic emulsion anonic emulsion anonic emulsion j should be used should be used should be used \

194

,. ■ ■ ■

TABLE 67

1 EMULSIFIED ASPHALT REQUIREMENT


Lbs. of emulsified asphalt per 100 lbs. of dry aggregate when percent passing No. 10 sieve Is:

50* 60 | 70 80 90 100

i 0 6.0 6.3 6.5 6.7 7.0 7.2

2 6.3 6.5 6.7 7.0 7.2 7.5

4 6.5 6.7 7.0 7.2 7.5 7.7

6 6.7 7.0 7.2 7.5 7.7 7.9

8 7.0 7.2 7.5 7.7 7.9 8.2

10 7.2 7.5 7.7 7.9 8.2 8.4

12 7.5 7.7 7.9 8.2 8.4 8.6

14 7.2 7.5 7.7 7.9 8.2 8.4

16 7.0 7.2 7.5 7.7 7.9 8.2

18 6.7 7.0 7.2 7.5 7.7 7.9

20 6.5 6.7 7.0 7.2 7.5 7.7

22 6.3 6.5 6.7 7.0 7.2 7.5

24 6.0 6.3 6.5 6.7 7.0 7.2

25 6.2 6.4 6.6 6.9 7.1 7.3

*50 or 1 ess.


195

TABLE 68



Pavement Temperature Index* Asphalt Grade, Penetration

Negative

0-40

40-100

Above 100

100-120

85-100

60-70

40-50

*The sum, for a 1 - year period, of the increments above 750F of monthly averages of the daily maximum temperatures. Average daily maximum temperatures for the period of record should be used where 10 or more years of record are available. For records of less than 10- year duration the record for the hottest year should be used. A negative index results when no monthly average exceeds 750F. Negative indexes are evaluated merely by subtracting the largest monthly average from 750F.

TABLE 69




Percent Asphalt by Weight of Dry Aggregate*

Rounded and Smooth

Angular and Rough

Intermediate

4

6

5

*Approximate quantities which may be adjusted in field based on' observation of mix and engineering Judgment.

196

■/,-■-

TABLE 70


p - 0.02 (a) + 0.07 (b) + 0.15 (c) + 0.20 (d)




c = percent of mineral aggregate passing No. 100 and retained on No. 200 sieve.

d = percent of mineral aggregate passing No. 200 sieve.

TABLE 71


Percent Passing

# 200 Sieve


Wet (5%+) Dry (0-5%)




*Soil should be pre-wetted with water before using these types of emulsified asphalts.

[after ü. S. Navy (22)]

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////// APPROXIMATE


APPROXIMATE \'EFFECTIVE RANGEv vOFANIONiC EMULSIONS v , \ \ \ \ \ \ \ \N

100% ALKALINE OR ALKALINE EARTH. OXIDE CONTENT

100%

FIGURE 51. Approximate effective range of catlonlc and anlonlc emulsions on various types of aggregates


207

TABLE 74


FOR BITUMINOUS STABILIZATION IN NONEXPEDIENT SUBGRADES


Environmental

Construction

When asphalt cements are used for bituminous stabilization, proper compaction must be obtained. If thin lifts of asphalt concrete are being placed, the air temperature should be 40eF and rising, and compaction equipment should be used Immediately after lay down operation. Adequate compaction can be obtained at freezing temperatures if thick lifts are utilized. When cutbacks and emulsions are utilized, the air temperature and soil temperature should be above freezing.^ Bituminous materials should completely coat the soil particles before rainfall stops construction.

Central batch plants, together with other specialized equipment, are necessary for bituminous stabilization with asphalt cements. Hot dry weather Is preferred for all types of bituminous stabilization.

208

TABLE 75


FOR CEMENT STABILIZATION IN NONEXPEDIENT SUBGRADES


Environnuintal

Construction

If the soil temperature is less than 60 to 70oF and is not expected to Increase for one month, chemical reactions will not occur rapidly, and strength gain of the cement- soil mixture will be minimal. If these environmental conditions are expected the cement may act as a soil modifier. Cement-soil mixtures should be scheduled for construction such that sufficient durability will be gained to resist any freeze-thaw cycles expected.

If heavy vehicles are allowed on the cement stabilized soils prior to a 10 to 1A day curing period, certain pavement damage can be expected.

209

- ■ tm n*miv<n v mnMMMflHMKMAi^.^-:" •-. ■

TABLE 76


FOR LIME STABILIZATION IN NONEXPEDIENT SUBGRADES


Environmental

Construction

If the soil temperature Is less than 60 to 70oF and is not expected to Increase for one month, chemical reactions will not occur rapidly, and the strength gain of the lime- soil mixture will be minimal. If these environmental conditions are expected the lime may act as a soil modifier. Lime-soil mixtures should be scheduled for construction such that sufficient durability will be gained to resist any freese-thaw cycles expected.

If heavy vehicles are allowed on the lime stabilized soils prior to a 10 to 14 day curing period, certain pavement damage can be expected.

210

■ ■.

TABLE 77



Crushed Stones and Sand Bitumen Soil Bitumen Sand-Gravel Bitumen


60-70 hot climate 40-50 hot climate 85-100 60-70 120-150 cold climate 85-100 cold climate

Cold Mix: Cold Mix: Cold Mix: Cutbacks Cutbacks Cutbacks

See Figure 49 See Figure 49 See Figure 49

Emulsions Emulsions Emulsions See Table 81 See Table 81 See Table 81 See Figures See Figures See Figures 50 and 51 to 50 and 51 to 50 and 51 to determine if determine if determine if a catonic or a catonic or a catonic or anonic emulsion anonic emulsion anonic emulsion should be used should be used should be used

211

TABLE 78



Lbs. of emulsified asphalt per 100 lbs. of dry aggregate when percent passing No. 10 sieve is:

50* 60 70 80 90 | 100

0 6.0 6.3 6.5 6.7 7.0 7.2

2 6.3 6 5 6.7 7.0 7.2 7.5

4 6.5 6.7 7.0 7.2 7.5 7.7

6 6.7 7.0 7.2 7.5 7.7 7.9

8 7.0 7.2 7.5 7.7 7.9 8.2

10 7.2 7.5 7.7 7.9 8.2 8.4

12 7.5 7.7 7.9 8.2 8.4 8.6

14 7.2 7.5 7.7 7.9 8.2 8.4

16 7.0 7.2 7.5 7.7 7.9 8.2

18 6.7 7.0 7.2 7.5 7.7 7.9

20 6.5 6.7 7.0 7.2 7.5 7.7

22 6.3 6.5 6.7 7.0 7.2 7.5

24 6.0 6.3 6.5 6.7 7.0 7.2

25 6.2 6.4 6.6 6.9 7.1 7.3

*50 or less.


212

TABLE 79


p = 0.02 (a) + 0.07 (b) + 0.15 (c) + 0.20 (d)




c ■ percent of mineral aggregate passing No. 100 and retained on No. 200 sieve.

d = percent of mineral aggregate passing No. 200 sieve.

213

TABLE 80

MARSHALL MIX DESIGN CRITERIA FOR'.


| Marshall Test


Minimum Maximum !

Stability, lbs.

Flow,(0.01 in.)

Percent air voids

750

7

3

16

5


TABLE 81


Percent 1 Passing

// 200 Sieve


Wet (5Z+) Dry (0-5%) |

1 0-5

| 5-15

| 15-25

SS-lh (or SS-Kh)

SS-1, SS-lh (or SS-K, SS-Kh)

SS-1 (or SS-K)

SM-K (or SS-lh*)

SM-K (or SS-lh*, SS-1*)

SM-K |



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0% SILICA CONTENT

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FIGURE 58. Approximate effective range of catlonlc and anlonlc emulsions on various types of aggregates


223

TABLE 83


FOR BITUMINOUS STABILIZATION IN NONEXPEDIENT BASE COURSES


Environmental

Construction

When asphalt cements are used for bituminous stabilization, proper compaction must be obtained. If thin lifts of asphalt concrete are being placed, the air temperature should be 40oF and rising, and compaction equipment should be used Immediately after lay down operation. Adequate compaction can be obtained at freezing temperatures if thick lifts are utilized. When cutbacks and emulsions are utilized, the air temperature and soil temperature should be above freezing. Bituminous materials should completely coat the soil particles before rainfall stops construction.

Central batch plants, together with other specialized equipment, are necessary for bituminous stabilization with asphalt cements. Hot dry weather is preferred for all types of bituminous stabilization.

224

;

TABLE 84


FOR CEMENT STABILIZATION IN NONEXPEDIENT BASE COURSES


Environmental If the soil temperature is less than 60 to 70oF and is not expected to increase for one month, chemical reactions will not occur rapidly, and strength gain of the cement- soil mixture will be minimal. If these environmental conditions are expected the cement may be expected to act as a soil modifier. Cement-soil mixtures should be scheduled for construction such that sufficient durability will be gained to resist any freeze-thaw cycles expected.

Construction If heavy vehicles are allowed on the cement stabilized soils prior to a 10 to 14 day curing period, certain pavement damage can be expected.

225

TABLE 85


FOR LIME STABILIZATION IN NONEXPEDIENT BASE COURSES


Environmental

Construction

If the soil temperature is less than 60 to 70oF and is not expected to increase for one month, chemical reactions will not occur rapidly, and the strength gain of the lime-soil mixture will be minimal. If these environmental conditions are expected the lime may be expected to act as a soil modifier. Lime-soil mixtures should be scheduled for construction such that sufficient durability will be gained to resist any freeze-thaw cycles expected.

If heavy vehicles are allowed on the lime stabilized soils prior to 10 to 1A day curing period, certain pavement damage can be expected.

226

TABLE 86



1 Crushed Stones and 1 Sand Bitumen j Soil Bitumen Sand-Gravel Bitumen


60-70 hot climate 40-50 hot climate 1 85-100 j 60-70 1 120-150 cold climate 85-100 cold climate

Cold Mix: Cold Mix: Cold Mix: Cutbacks Cutbacks Cutbacks

j See Figure 56 See Figure 56 See Figure 56

\ Emulsions Emulsions Emulsions | See Table 93 See Table 93 See Table 93

See Figures See Figures See Figures 57 and 58 to 57 and 58 to 57 arid 58 to

j determine if determine if determine if I a catonic or a catonic or a catonic or

anonic emulsion anonic emulsion anonic emulsion i should be used should be used should be used

227

TABLE 87



Lbs. of emulsified asphalt per 100 lbs. of when percent passing No. 10 sieve

dry aggregate Is:

50* 60 | 70 | 80 | 90 | 100

0 6.0 6.3 6.5 6.7 7.0 7.2

2 6.3 6.5 6.7 7.0 7.2 7.5

4 6.5 6.7 7.0 7.2 7.5 7.7

6 6.7 7.0 7.2 7.5 7.7 7.9

8 7.0 7.2 7.5 7.7 7.9 8.2

10 7.2 7.5 7.7 7.9 8.2 8.4

12 7.5 7.7 7.9 8.2 8.4 8.6

14 7.2 7.5 7.7 7.9 8.2 8.4

16 7.0 7.2 7.5 7.7 7.9 8.2

18 6.7 7.0 7.2 7.5 7.7 7.9

20 6.5 6.7 7.0 7.2 7.5 7.7

22 6.3 6.5 6.7 7.0 7.2 7.5

24 6.0 6.3 6.5 6.7 7.0 7.2

25 6.2 6.4 6.6 6.9 7.1 7.3

*50 or less.


228

TABLE 88



Pavement Temperature Index* Asphalt Grade, Penetration

Negative

0-40

40-100

Above 100

100-120

85-100

60-70

40-50

*The sum, for a 1 - year period, of the increments above 750F of monthly averages of the daily maximum temperatures. Average daily maximum temperatures for the period of record should be used where 10 or more years of record are available. For records of less than 10- year duration the record for the hottest year should be used. A negative index results when no monthly average exceeds 750F. Negative indexes are evaluated merely by subtracting the largest monthly average from 750F.

TABLE 89




Percent Asphalt by Weight of Dry Aggregate*

1 Rounded and Smooth

Angular and Rough

Intermediate

4

6 i 5

♦Approximate quantities which may be adjusted in field based on observation of mix and engineering judgment.

229

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TABLE 90

MIXTURE DESIGN CRITERIA

Marshall Criteria

Traffic Category Heavy Medium Light

Test Property Min. Max. Min. Max. Min. Max.

No. of Compaction Blows Each End of Specimen 75 50 35

Stability, all mixtures 750 500 500

Flow, all mixtures 8 16 8 18 8 20

Percent Air Voids Surfacing or Leveling 3 5 3 5 3 5 Base 3 8 3 8 3 8

Percent Voids in Mineral Aggregate

[after The Asphalt Institute (36)]

where: p

a

b

TABLE 91


p = 0.02 (a) + 0.07 (b) + 0.15 (c) + 0.20 (d)

percent of residual asphalt by weight of dry aggregate,

percent of mineral aggregate retained on No. 50 sieve.

c =

percent of mineral aggregate passing No. 50 and retained on No. 100 sieve.

percent of mineral aggregate passing No. 100 and retained on No. 200 sieve.

d = percent of mineral aggregate passing No. 200 sieve

230

TABLE 92

MARSHALL MIX DESIGN CRITERIA FOR'-


Marshall Test


Minimum Maximum

Stability, lbs.

Flow,(O.Ol in.)

Percent air voids

750

7

3

16

5


TABLE 93


Percent Passing

// 200 Sieve


Wet (5%+) Dry (0-5Z)





[after ü. S. Navy (22)]

231

TABLE 94

PORTLAND CEMENT ASSOCIATION CRITERIA FOR

SOIL-CEMENT MIXTURES USED IN BASE COURSES

Soil Classification Soil-Cement Weight

Loss During 12 Cycles of Either Wet-Dry Test

or Freeze-Thaw Test AASHO Unified*

A-1

A-2-4, A-2-5

A-3

GW, GP, GM SW, SP, SM

GM, GC, SM, SC

SP


| A-2-6, A-2-7

A-4

A-5

GM, GC, SM, SC

a, ML

ML, MH, OH


1 A-6

A-7

CL, CH

OH, MH, CH less than or equal to 7 percent

*based on correlation presented by Air Force (2)


232

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233

APPENDIX E

RAPID TEST PROCEDURES FOR EXPEDIENT CONSTRUCTION OPERATIONS USING SOIL-CEMENT STABILIZATION

Reproduced with permission of the Portland Cement Association (Ref. 10)

234

RAPID TEST PROCEDURES FOR EXPEDIENT CONSTRUCTION

OPERATIONS USING SOIL-CEMENT STABILIZATION*

A RAPID method of testing soil-cement has been used successfully for emergency construction and for

very small projects where more complete testing is not feasible or practical. The engineer applying this procedure should be familiar with the details of the ASTM-AASHO soil-cement test methods described in Chapter 3 so that he can properly interpret and evaluate the data obtained with this rapid method.

The following steps, which are described in more detail in the following paragraphs, are suggested:

1. Determine the maximum density and optimum moisture content for the soil-cement mixture

2. Mold specimens for inspection of hardness.

3. Inspea specimens using "pick" and "click" procedures.

Moisture-Density Test

The maximum density and optimum moisture content are determined at 12 per cent cement by weight by means of the modified moisture-density test procedure described in Chapter 3.

In instances where the standard mold and rammer are not available, tests can be made by using a 2-in. diameter filled-in gas pipe of sufficient length to weigh 3.5 lb. as the compacting rammer and a No. 2/2 tin can as the mold.

With experience the optimum moisture can be determined quite closely by "feel." When squeezed, soil-cement at optimum moisture will form a cast that will stick together when it is handled.

Molding Specimens

Specimens for inspection of hardness are molded by the same procedure described in Chapter 3. Thcje specimens generally contain 10, 14 and 18 per cent cement by weight. It is best if these specimens can be molded in the standard mold, and then removed from the mold and placed in high humidity for hydration.

However, if a standard mold is not available it is possible 10 mold these specimens in No. 2/3 tin cans, using the compacting rammer suggested above. The tin-can mold can

be torn or ripped from the hardened soil-cement specimens with pliers after a few days.

Inspecting Specimens

After at least a day or two of hardening, during which they are kept moist, and after a 3-hour soaking, the specimens are inspected by "picking" with a sharp-pointed instrument and by sharply "clicking" each specimen against a hard object such as concrete to determine their relative hardness when wet.

"Pick" Tetl

In the pick test, the specimen is held in one hand and a relatively sharp-pointed instrument, such as a dull ice pick, is lightly jabbed into the specimen (or the end of a specimen molded in a can) from a distance of two or three inches. If the specimen resists this light picking, the force of impact is increased until the pick is striking the specimen with considerable force. Specimens that are hardening satisfactorily will definitely resist the penetration of the pick.

NOT REPRODUCIBLE

The "pick" last.

*Since this material has been taken directly from the Portland Cement Associaticn text, figure numbers and certain other references in this Appendix may not be in agreement with other portions of this report.

235

whereas specimens that are not hardening properly will resist little. To pass the pick test, a specimen that is not over 7 days old and that has been soaked in water must prevent the penetration of the ice pick, which is under considerable force, to a distance greater than about one- eighth to ont'-quarter inch.

"Click" Test

The click test is then applied to water-soaked specimens that are apparently hardening satisfactorily and that have passed the pick test. In the click test, the specimens are held perpendicular to each other and about four inches apart, one in each hand. They are then lightly clicked together a number of times, the force of impact being increased with each click. Specimens that are hardening satisfactorily wi!l#

click together with a "ringing" or "solid" tone. As the force of impact is increased, one of the specimens may break transversely even though it is hardening adequately. The internal portion of a satisfactory specimen should then pass the pick test. When two or three hard specimens are once obtained they may be saved and one may be used in the click test with a soil-cement specimen of a soil in the process of being tested.

When a poorly hardened specimen is clicked with a satisfactory specimen, a "dull thud" sound is obtained rather than the "solid" sound obtained with two satisfactory specimens. After the first or second click the inferior specimen will generally break and its internal portion will not pass the pick test.

NOT REPRODUCIBLE

The "click" test.

At the time the click test is made, the age of the specimens must be taken into account. For instance, specimens that are not properly hardened at an age of 4 days may be satisfactorily hardened at an age of 7 days.

The above pick and click procedures are then repeated after the specimens have been dried out and again after a second soaking in order to test their relative hardness at both extremes of moisture content.

If equipment is available for making compression tests, these tests will provide further valuable data for study. It is suggested that duplicate specimens be molded and tested in compression at the age of 7 days and after a soaking in water for 4 hours. A satisfactory soil-cement mixture will have a compressive strength of about 400 lb. per sq.in. or more.

General Remarks

There is a distinct difference between satisfactorily hardened soil-cement specimens and • inadequately hardened specimens. Even an inexperienced tester will soon be able to differentiate between them and to select a safe cement content to harden the soil. It is important to remember that an excess of cement is not harmful but that a deficiency of cement will result in inferior soil-cement.

If the 10 and 14 per cent specimens are apparently hardening satisfactorily and compression-test data are favorable, the project can immediately be started using a cement content of 12 per cent by weight. If the quantities of cement available for construction are limited and if the 10 per cent cement specimens are hard and have good compressive strength, additional specimens should be molded at 8 per cent cement, be permitted to hydrate and then be tested in the same manner as the other specimens. If the 8 per cent cement specimens are satisfactorily hardened, the cement content being used in construction can be reduced to 10 per cent.

Should a 10 per cent specimen be comparatively soft at 4 days' hydration, while the 14 and 18 per cent specimens are hardening satisfactorily, construction should be started using 16 per cent cement by weight until additional data are obtained.

In some unusual instances, the 18 per cent cement specimen may not harden satisfactorily. The engineer then has two alternatives: (1) the effect of higher cement contents may be investigated to see whether 22 or 26 per cent cement will harden the soil; or (2) a borrow soil requiring a relatively low cement factor may be located and hauled to the runway or roadway to "cap" the poor soil. The latter proce- -luie will generally be the more economical one.

236

APPENDIX F

pH TEST ON SOIL-CEMENT MIXTURES

237

pH TEST ON SOIL-CEMENT MIXTURES

Materials;

I. Portland cement to be used for soil stabilization

Apparatus:

1. pH meter (the. pH meter must be equipped with an electrode having

a pH range of 14)

2. 150 ml. plastic bottles with screw-top lids

3. 50 ra1 . plastic beakers

4. Distilled water

5. Balance

6. Oven

7. Moisture cans

Procedure;

1. Standardize the pK meter with a buffer solution having a pH of 12.00.

2. Weigh to the nearest 0.01 gms., representative samples of air-dried

soil, passing the No. 40 sieve and equal to 25.0 gms. of oven-dried

soil.

3. Pour the soil samples into 150 ml. plastic bottles with screw-top lids,

4. Add 2.5 gms. of the portland cement.

5. Thoroughly mix soil and portland cement.

238

6. Add sufficient distilled water to make a thick paste. (Caution:

too much water will reduce the pH and produce an incorrect result.)

7. Stir the soil-cement and water until thorough blending is achieved.

8. After 15 minutes, transfer part of the paste to a plastic beaker

and measure the pH.

9. If the pH is 12.0 or greater, the soil organic matter content should

not interfere with the cement stabilizing mechanism. To determine

the required percent of cement, refer to design methods outlined in

Figure 23 or 24, as appropriate.

239

. .

APPENDIX G

DETERMINATION OF SULFATE IN SOILS

240


GRAVIMETRIC METHOD

Scope

Applicable to all soil types with the possible exception of soils

containing certain organic compounds. This method should permit the

detection of as little as 0.05% sulfate as SO.. 4

Reagents

1. Barium chloride, 10% solution of BaCl2 • 2H20. (Add 1 ml. 2%

HC1 to each 100 ml. of solution to prevent formation of carbonate.)

2. Hydrochloric acid, 2% solution (0.55 N)

3. Magnesium chloride, 10% solution of MgCl, ' 6H20

4. Demlneralized water

5. Silver nitrate, 0.1 N solution.

Apparatus

1. Beaker, 1000 ml.

2. Burner and ring stand

3. Filtering flask, 500 ml.

4. Büchner funnel, 9 cm.

5. Filter paper, Whatman no. 40, 9 cm.

6. Filter paper, Whatman no. 42, 9 cm.

7. Saran wrap

8. Crucible, ignition, or aluminum foil, heavy grade

241

9. Analytical balance

10. Aspirator or other vacuum source

Procedure

1. Select a representative sample of air-dried soil weighing

approximately 10 gm. Weigh to the nearest 0.01 gm. (Note:

When sulfate content is anticipated to be less than 0.1%,a sample

weighing 20 gm. or more may be used.) (The moisture content of

the air-dried soil must be known for later determination of dry

weight of the soil.)

2. Boil for 1 1/2 hours in beaker with mixture of 300 ml. water and

15 ml. HC1.

3. Filter through Whatman no. 40 paper, wash with hot water, dilute

combined filtrate and washings to 500 ml.

A. Take 100 ml. of this solution and add MgCl« solution until no

more precipitate is formed.

5. Filter through Whatman no. 42 paper, wash with hot water, dilute

combined filtrate and washings to 200 ml.

6. Heat 100 ml. of this solution to boiling and add BaCl. solution

very slowly until no more precipitate is formed. Continue boiling

for about 5 minutes and let stand overnight in warm place,

covering beaker with Saran wrap.

7. Filter through Whatman no. 42 paper. Wash with hot water until

free from chlorides (filtrate should show no precipitate when a

drop of AgNO- solution is added).

8. Dry filter paper in crucible or on sheet of aluminum foil. Ignite

paper. Weigh residue on analytical balance as BaSO,.

242

Calculation

%so . Weight of residue x ^ 6 A Oven-dry weight of initial sample

where

A.,«., J^ ., 4~u^ c J J^J t i Air-dry weight of initial sample Oven-dry weight of initial sample = i 6 c— .. Air-dry moisture content (%)

100%

Note

If precipitated from cold solution, barium sulfate is so finely

dispersed that it cannot be retained when filtering by the above

method. Precipitation from a warm, dilute solution will increase

crystal size. Due to the absorption (occlusion) of soluble salts

during the precipitation of BaSO. a small error is Introduced.

This error can be minimized by permitting the precipitate to digest

in a warm, dilute solution for a number of hours. This allows the

more soluble small crystals of BaSO, to dissolve and recrystallize

on the larger crystals.

243


TURBIDIMETRIC METHOD

Reagents;

1. Barium chloride crystals (Grind analytical reagent grade barium

chloride to pass a 1 mm sieve)

2. Ammonium acetate solution (0.5N). (Add dilute hydrochloric acid

until the solution has a pH of 4.2)

3. Distilled water

Apparatus;

1. Moisture can

2. Oven

3. 200 ml. beaker

4. Burner and ring stand

5. Filtering flask

6. Büchner funnel, 9 cm.

7. Filter paper, Whatman No. 40, 9 cm.

8. Vacuum source

9. Spectrophotometer and standard tubes (Bausch and Lomb Spectronlc 20

or equivalent) .

10. pH meter

244

Procedure;

1. Take a representative sample of air-dried soil weighing approximately

10 gms., and weigh to the nearest 0.01 gms. (The moisture content of the

air-dried soil must be known for later determination of dry weight of

the soil.)

2. Add the ammonium acetate solution to the soil. (The ratio of soil to

solution should be approximately 1:5 by weight.)

3. Boll for about 5 minutes.

4. Filter through Whatman No. 40 filter paper. If the extracting solution

is not clear, filter again.

5. Take 10 ml. of extracting solution (this may vary depending on the

concentration of sulfate in the solution) and dilute with distilled

water to about 40 ml. Add about 0.2 gm. of barium chloride crystals

and dilute to make the volume exactly equal to 50 ml. Stir for 1 minute.

6. Immediately after the stirring period has ended, pour a portion of the

solution into the standard tube and insert the tube into the cell of

the spectrophotometer. Measure the turbidity at 30 sec. intervals for 4

minutes. Maximum turbidity is usually obtained within 2 minutes and the

readings remain constant thereafter for 3-10 minutes. Consider the

turbidity to be the maximum reading obtained in the 4 minute interval.

7. Compare the turbidity reading with a standard curve and compute the

sulfate concentration (as SO.) in the original extracting solution. (The

standard curve is secured by carrying out the procedure with standard

potassium sulfate solutions.)

8. Correction should be made for the apparent turbidity of the samples by

running blanks in which no barium chloride is added.

245

Sattle Calculation:

Given: Wt. of alr-drled sample - 10.12 gms.

Water Content = 9.36%

Wt. of dry soil « 9.27 gms.

Total volume of extracting solution » ?9.1 ml.

10 ml. of extracting solution was diluted to 50 ml. after addition

of barium chloride (see step 5) . The solution gave a transmission

reading of 81.

Calculation:

From the standard curve, a transmission reading of 81 corresponds to 16.0 ppm.

(see following figure).

.'. Concentration of original extracting solution = 16.0 x 5 = 80.0 ppm.

- ef.— 80.0 x 39.1 x 100 n no,Q- % S04 " FOOO x 1000 x 9.27 " 0-0338%

Determination of Standard Curve;

1. Prepare'sulfate solutions of 0, 4, 8, 12, 16, 20, 25, 30, 35, 40, 45, 50

ppm. In separate test tubes. The sulfate solution Is made from potassium

sulfate salt dissolved In 0.5 N ammonium acetate (with pH adjusted to 4.2).

2. Continue Steps 5 and 6 in the procedure as described In Determination of

Sulfate In Soil by Turbldlmetrlc Method.

3. Draw standard curve as shown In following figure by plotting transmission

readings for known concentrations of sulfate solutions.

246

100

90„

80..'

CO

00

70..

o a:

60

50..

40 -H- 10

STANDARD CURVE BAUSCH AND LOMB SPECTRONIC 20 WAVE LENGTH = 420 NM DATE - JAN 4, 1971

f + •+■ 20 30 40

SULFATE CONCENTRATION, PPM

FIGURE 59. EXAMPLE STANDARD CURVE FOR SPECTROPHOTOMETER

50

247

APPENDIX H

SELECTION OF CEMENT CONTENT FOR CEMENT STABILIZED SANDY SOIL

Reproduced with permission of the Portland Cement Association (Ref. 10)

248

SELECTION OF CEMENT CONTENT FOR CEMENT STABILIZED SANDY SOIL *

THE following short-cut test procedures for sandy soils were developed as a result of a correlation made by the

Portland Cement Association of the data obtained from ASTM-AASHO tests on 2,438 sandy soils. These procedures do not involve new tests or additional equipment. Instead, some tests can be eliminated by the use of charts developed in previous tests on similar soils. The only tests required are a grain-size analysis, a moisture-density test and compressive-strength tests. Relatively small samples are needed. All tests, except for the 7-day compressive- strength tests, can be completed in one day.

Two procedures are used: Method A for soils not containing material retained on the No. 4 sieve and Method B for soils containing material retained on the No. 4 sieve. Method B was recently developed to permit the use of moisture-density data obtained on the total soil-cement mixture, as specified by the ASTM-AASHO moisture-density test methods revised in 1937.

The procedures can be used only with soils containing less than 30 per cent material smaller than 0.03 mm. (silt and clay) and less than 20 per cent material smaller than 0.003 mm. (clay). These were the gradation limits for the soils that were included in the correlation useJ to develop the original charts. Dark grey to black soils with appreciable amounts of organic impurities were not included in the correlation and therefore cannot be tested by these procedures. This is also true of miscellaneous granular materials such as cinders, caliche, chat, chert, marl, red dog, scoria, shale, slag, etc. Moreover, the short-cut procedures cannot be used with granular soils containing material retained on the No. 4 sieve if that material has a bulk specific gravity less than 2.43.

The short-cut test procedures do not always indicate the minimum cement factor that can be used with a particular sandy soil. However, they almost always provide a safe cement factor, generally close to that indicated by standard ASTM-AASHO wet-dry and freeze-thaw tests.

The procedures are being widely applied by engineers and bu'lders and may largely replace the standard tests when experience in their use is gained and the relationships are checked. The charts and procedures may be modified to conform to local climatic and soil conditions if necessary.

20 40 60 60 100 No 4 to No 60 sieve site material - per cent

Fig. 35. Average maximum densitiei of soil-cement mixtures not containing material retained on the No. 4 sieve.

Step-by-Stap Procedures Short-cut test procedures involve:

1. Running a moisture-density test on a mixture of the soil and portland cement.

2. Determining the indicated portland cement requirement by the use of charts.

3. Verifying the indicated cement requirement by compressive-strength tests.

Preliminary Sttpt

Before applying the short-cut test procedures, it is nee-

*Since this material has been taken directly from the Portland Cement Association text, figure numbers and certain other references in this Appendix may not be in agreement with other portions of this report.

249

essary ( 1 » to determine the gradation of the soil, and (2)

to determine the bulk specific gravity of the material re-

tained on the No. 4 sieve.* If all the soil passes the No. 4

sieve. Method A should be used. If material is retained on

the No. 4 sieve. Method B is used.

Method A Step 1: Determine by test the maxiinum density and

optimum moisture content for a mixture of the soil and

portland cement.* • Note I. Use Fig. 35 to obtain an estimated maximum

density of the soil-cement mixture being tested. This estimated maximum density and the percentage of material smaller than 0.05 mm. (No. 270 sieve) can be used with Fig. 36 to determine the cement content by weight to use for the test.

Step 2: Use the maximum density obtained by test in

Step 1 to determine from Fig. 36 the indicated cement

requirement.

Step 3; Use the indicated cement factor obtained in

Step 2 to mold compressive-strength test specimens* in

triplicate at maximum density and optimum moisture

content.

Step 4: Determine the average compressive strength

of the specimens after 7 days' moist-curing.

Step 5; On Fig. 37, plot the average compressive-

strength value obtained in Step 4. If this value plots above

the curve, the indicated cement factor by weight, deter-

mined in Step 2, is adequate.

For field construction, use Fig. 41 to convert

this cement content by weight to a volume basis.

Note 2: If the average compressive strength value plots below the curve of Fig. 37, the indicated cement factor obtained in Step 2 is probably too low. Additional tests will be needed to establish a cement requirement. These tests generally require the molding of two test specimens, one at the indicated cement factor obtained in Step 2 and one at a cement content two percentage points higher. The specimens are then tested by ASTM-AASHO freeze-thaw lest procedures.

Method B

Step 1; Determine by test the maximum density and

optimum moisture content for a mixture of the soil and

portland cement.** Not: 3: Use Fig. 38 to determine an estimated maxi-

mum density of the soil-cement mixture being tested. This estimated maximum density, the percentage of material

'The short-cut tests do not apply to soils containing more than 50 per cent silt and clay smaller than 0.05 mm. and more than 20 per cent clay smaller than 0.005 mm., or to dark grey or black organic soils. These soils, as well as miscellaneous granular materials such as cinders, caliche, chat, chert, marl, red dog, scoria, shale, slag, etc., and soils containing material retained on the No. 4 sieve having a bulk specific gravity less than 2.45 should not be used but should be tested by the ASTM-AASHO procedures. * 'Methods of Test for Moisture-Density Relations of Soil-Cement Mixtures, ASTM Designation D 558-57; AASHO Designation T134-57. tSpecimens of either 2-in. diameter and 2-in. height or 4-in. diameter and 4.6-in. height may be molded. The 2-in. specimens shall be submerged in water for one hour before testing and the 4-in. specimens for four hours. The 4-in. specimens shall be capped before testing. ttMethods of Test for Moiiture-Density Relations of Soil- Cement Mixtures, ASTM Designation D 558-57; AASHO Desig- nation T134-57.

Fig. 36. indicated cement contents of soil-cement mixtures not containing material retained on the No. 4 sieve.

100 10 15 20 25 30 35 40

Material smaller than 005 mm - per cent

45 50

250

• 300 n ■■ ■■ ; l^^^T^^" "*'4--""-—-^ i I SS ^^^^^ \ ^^K»^,,,,^ a i ^^0^

H 250 *?<. . L j ! \ " "

s? i

■ Kl K

E 200 1111 i 11 i 1111 1111 1 I 1 1 1 1 1 1 1 1 l i 1 1 MM MM M M 1 10 15 20 25 30 35

Motenol smaller than 0 05 mm- percent

40 45 50

Fig. '17. Minimum 7-day compressive strengths required for soil-cement mixtures not containing material retained on the No. 4 sieve.

smaller than 0.05 mm (No. 270 sieve), and the percentage of material retained on the No. 4 sieve can be used with Fig. 39 to determine the cement content by weight to use in the test.

The soil sample for the test shall contain the same percentage of material retained on the No. 4 sieve as the original soil sample contains, except that a maximum of 43 per cent is used. Also, %-in. material is the maximum size used. Should there be material larger than this in the original soil sample, it is replaced in the test sample with an equivalent weight of material passing the ^4-in. sieve and retained on the No. 4 sieve.

Step 2: Use the maximum density obtained by test in Step 1 to determine from Fig. 39 the indicated cement requirement.

Step 3; Use total material as described in Step 1 and the indicated cement factor obtained in Step 2 to mold compressive-strength test specimens* in triplicate at maximum density and optimum moisture content.

Step 4: Determine the average compressive strength of the specimens after 7 days' moist-curing.

Step 5: Determine from Fig. 40 the minimum allowable compressive strength for the soil-rement mixture. If the average compressive strength obtained in Step 4 equals or exceeds the minimum allowable strength, the indicated cement factor by weight obtained in Step 2 is adequate.

For field construction, use Fig. 41 to convert this cement content by weight to a volume basis.

Note 4: If the average compressive-strength value is lower than the minimum allowable, the indicated cement factor obtained in Step 2 is probably too low. Additional tests as described in Note 2 are needed.

Example of Use of Short-Cut Test Procedures

Following is an example of the use of the short-cut procedures.

'Specimens of 4-in. diameter and 4.6-in. height shall be molded. They shall be submerged in water for four hours and shall be capped before testing.

Preliminary tests determine the gradation of the soil and bulk specific gravity of the material, if any, retained on the No. 4 sieve. The data obtained from the tests are tabulated below. In this example. Method B should be used since the soil contains material retained on the No. 4 sieve.

Gradation:

Passing

No. 4 sieve 82 per cent No. 10 sieve 77 per cent No. 60 sieve 58 per cent No. 200 sieve 37 per cent

70

60

S 50

40

30

20

10

0 10 20 30 40 50

Motenol smolier thon 0 05 mm - per cent

Fig. ih. Average maximum densities of soil-cement mixtures containing material retained on the No. 4 sieve.

/

1 \

K j. /

r

\ / / N

k ̂ _o y

/ —

y/ < t A

k 6 */ / -N ♦ — ■ '-JUS'

/ y i 1

L J^ <

i i V\ i

i i

i i !

i

251

Smaller than 0.05 mm. (silt and clay

combined) M per cent 0.005 mm. (clay) 13 per cent

Color; Brown

Bulk specific gravity of material retained on No. 4 sieve: 2.50.

Step /.' Fig. 38 indicates that the estimated maximum density of the soil-cement mixture is 122 lb. per cu.ft since the soil contains 32 per cent material smaller than 0,05 mm. and 23 per cent material retained on the No. 10 sieve.

Fig. 39 is used to determine the cement content by weight to use in the moisture-density test. Since the soil contains 32 per cent material smaller than 0.05 mm. and 18 per cent matc'ial retained on the No. 4 sieve, and since the estimated maximum density is 122 lb. per cu.ft., 6 per cent cement by weight is indicated.

Perform the moisture-density test. For this example, assume the maximum density obtained

by test to be 123.2 lb per cu.ft at 10.2 per cent moisture.

Step 2: Fig. 39 indicates a cement factor of 6 per cent.

using the calculated actual density of 123.2 lb. per cu.ft.

Step 3: Using total material and 6 per cent cement by weight, mold compressive-strength test specimens in triplicate at maximum density (123.2 lb. per cu.ft.) and optimum moisture (10.2 per cent).

Step 4: Determine the average 7-day compressive strength.

For this example, assume the average compressive strength to be 345 psi.

Step 5; Since the soil contains 32 per cent material smaller than 0.05 mm. and 18 per cent material retained on the No. 4 sieve, the minimum allowable compressive strength for this soil-cement mixture is 280 psi, as shown in Fig. 40. The average compressive strength of the mixture used in this example (345 psi), as obtained in Step 4, is higher than the minimum allowable strength. Therefore, the indicated cement content of 6 per cent by weight is adequate.

For field construction, Fig. 41 shows that 6 per cent cement by weight is equivalent to 7.4 per cent cement by volume.

If the average compressive strength in Step 4 had been

Fig. 39. Indicoted cement contents of ioii-cement mixture! containing material retained on the No. 4 tiev«.

13 , 12 , 11 Cement content by weigh ■ 10 , 9 .

- per cent 8,7,6,5.

T 0/ 11' jvi r -X' U V', L'X- V^L -1S*.\- 1 : jm. :JM r

Vot .- VJ--- Vb> 'r. \ V' \Ki \ S^ ^ 'V M ft \ \ :iii\iiii!'\!i \ \ A \

fwfli \ '\ ^ jL i S- "?IB

v. Ill \ S ♦ \V-2. JL L rtr^t v i sXt A

i

- P - - - ptt. i -11 \

. \ r SL i% 4:::^.:J::^/_^

i 20 I

i y 1 ! \ uo > <JO rf

mm nimr, J : rs . / , \ i y/ /f ij \ i \

-V'wfe / J{\/ V \ t

j ^-V^-'r^r 7s t riX / r\jr

"x^s ^ tA | "> ^ jn /'jy^ r wn 5^ ". S:"l::js 1^». iM. V^ ^ ( [ J/^ K

c 1 A \ \

r^ SJ^ 1 \ \ \ r lit"" I_L^TT '"^"hrk-Ttt"' Vl 1 i ^ii: _:5: ^

V t .- S^ it S it . 1 ' .X Li rTTrxn^rrnirxr, i._4:__i 0 5 10 15 20 25 30 39 <0 49 9C

40

30

20

10

0

Material smaller tnan 0 05 mm -percent

252

so ■

40-

30-

= 20- o E

10 •

■ -^^ o

15

-40

— 30

■20

Fig. 40. Minimum 7-day compretiive strength» required for soil-cement mixtures containing material retained on the No. 4 sieve.

lower than the minimum allowable strength, say 243 psi, 6 per cent cement by weight probably would not have been adequate. Additional testing would then have been required to establish the cement requirement for the soil.

These tests would involve molding and testing freeze-thaw test specimens according to ASTM-AASHO procedures. Freeze-thaw specimens containing 6 and 8 per cent cement by weight would probably be adequate in this instance.

253

, .■>.■■

-100

-105

■110

•115

-120

-125

-130

-135

H8

H7

-16

-15

14

t-13

I?

-II

HO

-9

-8

3

•140

'-KS

•7 ►-■

-6

-5

-4

r-ie

rl5

i-14

-13

HZ

HI

HO

-9

-8

-7

-6

-5

"-3 Fig. Al R«la»ion of ctment content by weight of oveiidry toil to cement content by volume of compacted «oil-cement mixture.

25A

APPENDIX I

SELECTION OF CEMENT CONTENT FOR BASE COURSE SOIL-CEMENT MIXTURES

(Reproduced with permission of the Portland Cement Association (Ref. 10)

255

SELECTION OF CEMENT CONTENT FOR BASE

COURSE SOIL-CEMENT MIXTURES*

THIS chapter will be of major interest to the laboratory engineer because it will assist him in determining what

cement contents to investigate in the soil-cement tests. The field engineer and administrative engineer will also be in- terested because the properties of soil-cement mixtures and the relationships existing among these properties and various test values are discussed. Information is presented that will enable engineers to estimate probable cement factors so that job estimates can be made before any tests are made.

In order to obtain the maximum amount of information from the wet-dry and freeze-thaw tests, it is important that the laboratory engineer design the soil-cement specimens properly. For instance, if specimens are designed with very high cement contents, they will all pass the wet-dry and freeze-thaw tests: and a minimum cement factor will not have been determined. On the other hand, if the specimens are designed with inadequate cement contents, they will all fail in the tests.

The principal requirement of a hardened soil-cement mixture is that it withstand exposure to the elements. Strength might also be considered a principal requirement; however, since most soil-cement mixtures that possess adequate resistance to the elements also possess adequate strength, this requirement is secondary.

Therefore, in a study to determine when a certain soil- cement mixture has been adequately hardened, the requirement of adequate resistance to exposure is the first considered. That is, will the hardened soil-cement mixture withstand the wetting and drying and the freezing and thawing cycles of nature and still maintain at least the stability inherent in the mass at the time the roadway was opened to traffic?

For instance, consider a hypothetical road subgrade made from a clay loam soil without cement, packed to maximum density at a moisture content slightly less than its optimum moisture content. This mass can withstand relatively heavy loads without failure, although it cannot offer much resistance to abrasive forces.

The same soil mixed with cement and compacted to maximum density at optimum moisture content will have stability before the cement hydrates at least equal to that of the raw soil.

But consider the two cases at a later date under a condi-

tion of slow drainage when moisture, by capillary action or in some other manner, has permeated the masses. The voids in the raw soil become filled with water and t^e soil loses the original inherent physical stability that was built into it by compaction to maximum density. This is not so, however, with the adequately hardened soil-cement mixture, which has continually increased in stability since its construction because of cement hydratton and resultant cementation. Its air voids will become filled with water too, but its stability will still be much greater than that built into it originally.

The next important requirement to consider is economy. Available data indicate that about 83 per cent of all soils likely to be used for soil-cement can be adequately hardened by the addition of 14 per cent cement or less. To determine whether or not a soil falls into this category would not require much testing. However, more than 30 per cent of all soils so far tested for soil-cement require only 10 per cent cement or less for adequate hardening. To identify these soils requires more testing. Since soil- cement is in the low-cost paving field, the testing engineer on large jobs should determine by test the minimum quantity of cement that can be safely used with each soil. By this procedure the lowest-cost soil-cement construction possible will be obtained.

Estimating Cement Requirements

The following information will aid the engineer in estimating cement requirements of the soils proposed for use and in determining what cement factors to investigate in the laboratory tests.

As a general rule, it will be found that the cement requirement of soils increases as the silt and clay content increases, gravelly and sandy soils requiring less cement for adequate hardness than silt and clay soils.

The one exception to this rule is that poorly graded, one- size sand materials that are devoid of silt and clay require more cement than do sandy soils containing some silt and clay.

In general, a well-graded mixture of stone fragments or gravel, coarse sand, and fine sand either with or without small amounts of feebly plastic silt and clay material will

*Since this material has been taken directly from the Portland Cement Association text, figure numbers and certain other references la this Appendix may not be in agreement with other portions of this report.

256

require 5 per cent or less cement by weight. Poorly graded one-size sand materials with a very small amount of nonplastic silt, typical of beach sand or desert blow sand, will require about 9 per cent cement by weiglr. The remaining sandy soils will generally require about 7 per cent. The nonplastic or moderately plastic silty soils generally require about 10 per cent cement by weight, and plastic clay soils require about 13 pet cent or more.

Table 1 gives the usual range in cement requirements for subsurface soils of the various AASHO* soil groups. "A" horizon soils may contain organic or other material detrimental to cement reaction and may require higher cement factors. For most A horizon soils the cement content in Table 1 should be increased four percentage points if the soil is dark grey to grey and six percentage points if the soil is black. It is usually not necessary to increase the cement factor for a brown or red A horizon soil. Testing of "poorly reacting" sandy surface soils is discussed in detail in Chapter 8. These cement contents can be used as preliminary estimates, which are then verified or modified as additional test data become available.

St*p-by-Step Procedure

The following procedure will prove helpful to the testing engineer in setting up cement contents to be investigated:

Step 1: Determine from Table 1 the preliminary estimated cement content by weight based on the AASHO soil group.

Step 2; Use the preliminary estimated cement content obtained in Step 1 to perform the moisture-density test.

Step 3: Verify the preliminary estimated cement content

'Charts and tables for use in classifying soils by the American Association of State Highway Officials Soil Classification System (AASHO Designation: M 145-49) are given in the appendix.

TABLE 1. Cement Requirements of AASHO Soil Groups

Usual rang« Eitifnatsd cuiw.i

AASHO Mil

in cmiMit content and that Conwnt conlonti rtquiraimnl mod in ^

moisturo-dtnuty for wol-dry and

per «nl par cent Ml. -1 por cont by wt. by vol. by wt. por cont by wt.

A-l-a 5- 7 3- 3 i 3-5-7 j A-l-b 7-9 5- 8 i 4- 6- 8 A-2 7-10 5- 9 7 5-7-9 j A-3 8-12 7-11 9 7- 9-11 ( A-4 8-12 7-12 10 8-10-12 A-5 8-12 8-13 10 8-10-12 A-6 10-14 9-1S 12 10-12-14 A-7 10-14 10-16 13 11-13-15 |

by referring to Table 2 if the soil is sandy or to Table 3 if it is silty or clayey. These tables take into consideration the maximum density and other properties of the soil, which permits a more accurate estimate. In the case of A horizon soils, the indicated cement factor should be increased as discussed above for Table 1. Sandy soils:

(1) Using the percentage of material smaller than 0.03 ■.;:.., the percentage of material retained on the No. 4 sieve, and the maximum density obtained by test in Step 2, determine from Table 2 the estimated cement content. (2) Mold wet-dry and freeze-thaw test specimens at the estimated cement content by weight obtained in (I) and at cement contents two percentage points above and below that cement factor.

Silty and clayey soils: (1) Using the percentage of material between

TABUE 2. Average Cement Requirements of B and C Heriien Sandy Selb

moranai rSioinvfl OH No. 4 stovo,

por cont

Miiierfjil muivnai •malltr

tnon 0.05 mm.,

por conl

Comont canlonl, por cont by wt.

105-10» 110-114 Maximum donsl

115-119 ly. lb. por cu.fl.

120-124 125-129 130 or rnora |

0-14 0-19

20-39 40-50

10 9

11 10

8 7 9

15-29 0-19

20-39 40-5Ü

10 9

12 10

8 7 9

30-45 0-19

20-39 40-50

10 11 12 11

7 8

10

257

T^BLE 3. Average Cement Requirements of R and C Horizon Silty and Clayey Soils

Material Cement content, per c«ni by wt. between 0.05 mm.

AASHO and Moximum density, lb. per cu.ft. group 0 005 mm., in(i»K per cent

0-19

90-94

1?

95-99

11

100-104 i 105-109

10 8

110-114 115-119 120 or mora

8 7 7 m JV 1? 1 1 10 9 8 8 7

0- 3 40- 59 13 12 n 9 9 8 8 60 or i'wnp. — — — —

i 0-19 13 12 _

8 7 7 20-39 13 12 10 9 8 8

4-- 7 40-59 14 13 10 10 9 8 60 or more 15 14 11 10 9 9

0-19 14 13 _ ..

10 9 8 8 20-39 15 14 10 9 9 9

8-11 40-59 16 14 11 10 10 9 60 or mor« 17 15 11 10 10 10

0-19 15 14 12 11 9 9 20 39 16 15 12 11 10 10

12-15 40-59 17 16 12 12 11 10

... 60 or more

0-19

18

17

16

16 14

13 12 11 11

13 12 11 10 20-39 18 17 14 13 11 11

16-20 40-59 19 18 14 14 12 12 60 or more 20 19 16 15 14 13 12

0.05 mm. irul 0 005 mm., the AASHO group index, and the tmxirnum density obtained by test in Step 2, determine from Table 3 the estimated cement content. (2) Mold wet-dry and freeze-thaw test specimens at the estimated cement content obtained

in (1) and at cement contents two percentage points above and below that cement factor.

To help in determining how well the soil reacts, it is advantageous to save half of the last moisture-density test specimen and to place it in an atmosphere of high humidity for inspection daily. This half specimen, called the

Fig. 5. Soil-cement specimens saved from tail end of moisture-density test procedure. Rate of hardening of the soil-cement mixture is investigated from day to day with a dull-pointed instrument.

NOT REPRODUCIBLE

258

"tail-end" specimen (see Fig. 5;, is obtained during the usual procedure of cutting the last specimen of the moisture-density test in half vertically (details are given on page 20) so that a representative moisture sample can be taken. The criteria used in the rapid test procedure, as discussed in Chapter 7, can be used to judge the hardness of the tail-end specimen. Generally, tail-end specimens are satisfactorily hardened in two to four days and it is not uncommon for them to be satisfactory a day after molding.

A study of compressivestrength data, as discussed in Chapter 4, is also helpful in checking the estimated cement factor

Miscellaneous Soils A number of miscellaneous materials or special types of soils, such as caliche, chert, cinders, scoria, shale, etc., have been used successfully in soil-cement construction. In some cases these materials have been found in the roadway or street that was to be paved with soil-cement; in other cases, in order to reduce the cost of the project, they have been used as borrow materials to replace soils that required high cement contents for adequate hardening.

The procedure for testing miscellaneous materials is the same as that used for regular soils. Average cement requirements of a number of miscellaneous materials and

cement contents to be investigated in the laboratory tests are given in Table 4. As test data are accumulated and experience is gained with local miscellaneous materials, it may be found that future testing can be reduced or eliminated fot similar materials.

TABLE 4. Average Cement Requirements of Miscellaneous Materials

Etlimoltd camant conttnl and thai Ctmanl conltnt«

Typt of «»ad in tor wat-dry and miMcllaiweui moittura-daniitir fraaia-thaw

material IMI fatti. par cant par canl par cant by wl. by vol. by wl.

Shall «oili 1 7 5- 7- 9 Umttlon« tcrttntngs 7 3 3- 5- 7 Rad dog 9 8 6- 810 Shalt ar ditintagraltd 1

ihalt 1) 10 8-10-12 Callcht 3 7 5- 7- 9 Clndan 8 t 6- 8-10 Chart 9 8 6- 8-10 Choi 8 7 5- 7- 9 Marl II II 9 11-13 Scoria conlaining ma

larial raloinad on lha No. 4 iiava 12 II 911-13

Scoria not conlaining malarial rtlaintd oh lha No. 4 liava 8 7 5- 7- 9

Alr-coolad «log 9 7 5- 7- 9 Wolar-coolad tlog 10 12 1012-14

259

APPENDIX J

pH TEST TO DETERMINE LIME REQUIREMENTS FOR LIME STABILIZATION

260

pH TEST TO DETERMINE LIME REQUIREMENTS

FOR LIME STABILIZATION

Materials:

1. Lime to be used for soil stabilization

Apparatus:

1. pH meter (the pH meter must be equipped with an electrode

having a pH range of 14)

2. 150 ml. (or larger) plastic bottles with screw-top lids

3. 50 ml. plastic beakers

4. CO2 - free distilled water

5. Balance

6. Oven

7. Moisture cans

Procedure:

1. Standardize the pH meter with a buffer solution having a pH of 12.45.

2. Weigh to the nearest 0.01 gms. representative samples of air-dried

soil, passing the No. 40 sieve and equal to 20.0 gms. of oven-

dried soil.

3. Pour the soil samples Into 150 ml. plastic bottles with screw-top lids.

261

4. Add varying percentages of lime, weighed to the nearest 0.01 gm,

to the soils. (L,ime percentages of 0, 2, 3, 4, 5, 6, 8 and 10,

based on the dry soil weight,, may be used.)

5. Thoroughly mix soil and dry lime.

6. Add 100 ml, of C0„ - free distilled water to the soil-lime mixtures.

7. Shake the soil-lime and water for a minimum of 30 seconds or until

there is no evidence of dry material on the bottom of the bottle.

8. Shake the bottles for 30 seconds every 10 minutes.

9. After one hour, transfer part of the slurry to a plastic beaker and

measure the pH.

10. Record the pH for each of the soil-lime mixtures. The lowest

percent of lime giving a pH of 12.40 is the percent required to

stabilize the soil. If the pH does not reach 12.40, the minimum

lime content giving the highest pH is that required to stabilize the

soil.

262

REFERENCES

1. Lambe, T. W., Foundation Engineering, edited by G. A. Leonards, McGraw-Hill Book Co., 1962.

2. Department of the Air Force, "Materials Testing," AFM 88-51, February 1966.

3. Johnson, A. W., "Soil Stabilization," Technical Bulletin No. 258, American Road Builders Association, 1965.

4. Department of the Army, "Soil Stabilization for Roads and Streets," Technical Manual TM 5-822-4, (also Air Force Manual 88-7), Chap. 4, June 1969.

5. Oglesby, C. H. and L. I. Hewes, Highway Engineering, John Wiley and Sons, Inc., New York, 1963. --■ ~~^-—-*.— -

6. Robnett, Q. L. and M. R. Thompson, "Stabilization of Illinois Materials- Development of Guidelines and Criteria," Illinois Cooperative Highway Research Program Project IHR-94, September 1969.

7. "PCA Soil Primer," Portland Cement Association, 1962.

8. Thompson, M. R. and Q. L. Robnett, "Second Air Force Stabilization Colloquium," Kirtland Air Force Base, February 1970.

9. Kelley, Conard M. and K. A. Gutschick, personal conversation, June 1970.

10. "Soil-Cement Laboratory Handbook," Portland Cement Association.

11. Robbins, E. G., personal conversation, June 22, 1970.

12. "Lab Studies Set Coarse Grading Limits for Soil-Cement," Soil Cement News, No. 84, Portland Cement Association, January 1966.

13. "Bituminous Base Course Practices," Highway Research Board Committee MC-47, Bituminous Aggregate Bases, presented at 49th Annual Meeting HRB, 1970.

14. Winterkorn, H. F., "Granulometric and Volumetric Factors in Bituminous Soil Stabilizatipn," Proceedings, Highway Research Board, 1957.

15. "Stabilization of Soil with Asphalt," Technical Bulletin No. 200. American Road Builders Association, 1953.

263

16. "Asphalt Mixed-in-Place (Road Mix) Manual," Manual Series No. 14, The Asphalt Institute, May 1965.

17. Herrin, M., "Bituminous-Aggregate and Soil Stabilization," Highway Engineering Handbook, Section 111, Editor, K. B. Woods, McGraw-Hill Book Co., 1960.

18. Robnett, Q. L. and M. R. Thompson, "Stabilization Recommendations for Illinois Soils and Materials," Illinois Cooperative Highway Research Program, Project IHR-94, August, 1969.

19. "Specifications for Emulsified Asphalt Treated Base Course," Revised August 1958, Pacific Division, The Asphalt Institute, 1958.

20. "Bitumuls Base Treatment Manual," Chevron Asphalt Company, 19b7 with supplement 1969.

21. Dunning, R. L. and F. E. Turner, "Asphalt Emulsion Stabilized Soils as a Base Material in Roads," Proceedings, Association of Asphalt Paving Technologists," Vol. 34, 1965.

22. U.S. Naval Civil Engineering Laboratory, "A Guide to Short-Cut Procedures for Soil Stabilization with Asphalt," Technical Note N955, April 1968.

23. "Standard Specifications for Road and Bridge Construction," Texas Highway Department, 1962.

24. "Standard Specifications," California Division of Highways, January 1969.

25. Department of the Army, "Flexible Airfield Pavements—Air Force, Airfields other than Army," Technical Manual TM 5-824-2, August 1959.

26. Robnett, Q. L. and M. R. Thompson,"Soil Stabilization Literature Reviews," Illinois Cooperative Highway Research Program, Project IHR-94, June 1969.

27. "Lime Treated Asphalt," Texas Contractor, March 7, 1961.

28. "Hydrated Lime in Asphalt: Paving," Bulletin No. 325. National Lime Association.

29. Hindermann, W. L., "Hydrated Lime in Asphalt Paving," Pit and Quarry, May 1969.

30. Department of the Army, "Soil Stabilization-Emergency Construction," Technical Manual TM 5-887-5, (also Air Force Manual AFM 88-40), Chap. 30, May 1966.

31. Mertens, E. W. and Wright, "Cationic Asphalt Emulsions: How They Differ from Conventional Emulsion in Theory and Practice," Proceedings, Highway Research Board, Vol. 38, 1959. "

264

32. Oklahoma Highway Department, "Engineering Classification of Geologie Materials," Oklahoma Highway Department Research and Development Division, 1967.

33. McKesson, C. L., "Suggested Method of Test for Bearing Value of Sand- Asphaltic Mixtures," Procedure for Testing Soils, ASTM, 1950.

34. Bird, G. C., "Stabilization Using Emulsified Asphalt," Proceedings, Canadian Good Roads Association, 1959.

35. "Method of Test for Centrifuge Kerosene Equivalent Test," Test Method No. Calif. 303-E. Materials Manual, California Division of Highways, 1966.

36. "Mix Design Methods for Asphalt Concrete and Other Hot-Mix Types, Manual Series No. 2, The Asphalt Institute, October 1969.

37. Warden, W. B. and S. B. Hudson, "Hot-Mixed Black Base Construction Using Natural Aggregate," Proceedings, Association of Asphalt Paving Technologists, Vol. 30, 1961.

38. McDowell, C. and A. W. Smith, "Design, Control and Interpretation of Tests for Bituminous Hot Mix Black Base Mixtures," Texas Highway Department, TP-8-69-E, March 1969.

39. Monismith, C. L., "Asphalt Paving Technology—Some Current Developments and Trends," Civil Engineering, ASCE, August 1969.

40. Monismith, C. L., "Design Considerations for Asphalt Pavements," First Conference on Asphalt Pavements for Southern Africa, Durban, Republic of South Africa, July 1969.

41. Killas, B. F., "Dynamic Modulus of Asphalt Concrete in Tension and Tension-Compression," Proceedings, Association of Asphalt Paving Technologists, January 1970.

42. Majidzadeh, K., D. V. Ramsamooj and T. A. Fletcher, "Analysis of Fatigue of a Sand-Asphalt Mixture," Proceedings, Association of Asphalt Paving Technologists, Vol. 38, 1969.

43. Terrel, R. L. and C. L. Monismith, "Evaluation of Asphalt-Treated Base Course Materials," Proceedings, Association of Asphalt Paving Technologists, 1968.

44. Epps, Jon A., "Influence of Mixture Variables on the Flexural Fatigue and Tensile Properties of Asphalt Concrete," Thesis, U. of California, Berkeley, 1968.

45. Davies, J. R. and J. A. Stewart, "An Investigation of the Strength Properties of Sand-Emulsified Asphalt Mixtures," D.H.O. Report No. RR146, Ontario Joint Highway Research Programme, June 1969.

265

. •■ .. . .

46. Puzinauskas, V. P. and B. F. Kallas, "Stabilization of Fine-Grained Soils with Cutback Asphalt and Secondary Additives, Bulletin 309, Highway Research Board, 1962.

47. Herrin, M., "Drying Phase of Soil-Asphält Construction," Bulletin 204, Highway Research Board, 1958.

48. Brahma, S. P., "Influence of Curing of Cutback Asphalt on Strength and Durability of Asphalt Concrete," Highway Research Record 256, Highway Research Board, 1968.

49. LeFebvre, J. A., "A Suggested Marshall Method of Design for Cutback Asphalt-Aggregate Paving Mixtures," presented at Annual Meeting of the Canadian Technical Asphalt Association, 1966.

50. McKesson, C. L. and A. W. Mohr, "Soil-Emulsified Asphalt and Sand- Emulsified Asphalt Pavement," Proceedings, Highway Research Board, Vol. 21, 1941.

51. Katti, R. K., D. T. Davidson and J. B. Sheeler, "Water in Cutback Asphalt Stabilization of Soil," Bulletin 241, Highway Research Board, 1960. '

52. Uppal, I. S., "Soil-Bituminous Stabilization," Highway Research Record 198, Highway Research Board, 1967.

53. Benson, J. R. and C. J. Becker, "Exploratory Research in Bituminous Soil Stabilization," Proceedings, Association of Asphalt Paving Technology, Vol. 13, 1942.

54. Endersby, V. A., "Fundamental Research in Bituminous Soil Stabilization," Proceedings, Highway Research Board, Vol. 22, 1942.

55. Riley, J. C. and G. C. Blomqulst, "Asphalt Stabilization of Selected Sand and Gravel Base Courses," Circular No. 46, Highway Research Board, September, 1966.

56. "Recommended Procedures and Specifications for Asphalt-Treated Soil Bases," Specification PCD No. 6, The Asphalt Institute, Pacific Coast Division, June 1964.

57. Finn, F. N., R. G. Hicks, W. J. Karl, and L. D. Goyne, "Design of Emulsified Asphalt Treated Bases," prepared for presentation at 1969 Annual Meeting of Highway Research Board.

58. Karl, W. J., "Design of Emulsified Asphalt Treated Base Course," First Conference on Asphalt Pavements for South Africa, Durban, Republic of South Africa, July 1969.

59. "Soil Stabilization with Portland Cement," Bulletin 292, Highway Research Board, 1961.

266

60. MacLean, D. J. and P. T. Sherwood, "Study of the Occurrence and Effects of Organic Matter in Relation to the Stabilization of Soils with Cement," Proceedings, Fifth International Conference on Soil Mechanics and Foundation Engineering, 1961.

61. Thompson, M. R., "The Significance of Soil Properties in Lime-Soil Stabilization," Civil Engineering Studies, Highway Engineering Series No. 13, University of Illinois, June 1964.

62. Robblns, E. G. and P. E. Mueller, "Development of a Test for Identifying Poorly Reacting Soils Encountered in Soil-Cement Construction, Bulletin 267, Highway Research Board, 1960.

63. Robbins, E. C, personal conversation, June 1970.

64. Catton, M. D. "Research on the Physical Relations of Soil and Soil-Cement Mixtures," Proceedings, Highway Research Board, 1940.

65. Clare, K. E. and P. T. Sherwood, "The Effect of Organic Matter on the Setting of Soil-Cement Mixtures," Journal of Applied Chemistry, Vol. 4, Nov. 1954 " ~ "" ~ ~

66. Sherwood, P. T., "The Effect of Sulphates on Cement-Stabilized Clay," Bulletin 198, Highway Research Board, 1958.

67. Felt, E. J., "Factors Influencing Physical Properties of Soil Mixtures," Bulletin 108, Highway Research Board, 1955.

68. Davidson, D. T. and B. W. Bruns, "Comparison of Type I and Type II Portland Cements for Soil Stabilization," Bulletin 267, Highway Research Board, 1960.

69. Care, K. E. and A. E. Pollard, "The Relationship Between Compressive Strength and Age for Soils Stabilized with Four Types of Cement," Magazine of Concrete Research, December 1951,

70. "Specifications for Portland Cement," (C 150), Part 10, Concrete and Mineral Aggregates, ASTM, 1967.

71. Leadabrand, J. A. and L. T. Norling, "Soil-Cement Test Data Correlation in Determining Cement Factors for Sandy Soils," Bulletin 69, Highway Research Board, 1953.

72. Leadbrand, J. A. and L. T. Norling, "Simplified Methods of Testing Soil-Cement Mixtures," Bulletin 122, Highway Research Board, 1956.

73. Norling, L. T. and R. G. Packard, "Expanded Short-Cut Methods for Determining Cement Factors for Sandy Soil," Bulletin 198, Highway Research Board, 1958.

74. "Soil-Cement Construction Handbook," Portland Cement Association, 1956.

267

75. U.S. Naval Civil Engineering Laboratory, "Short-Cul: Procedures for Soil CemenL Construction In Sandy Soil," October 1966.

76. Diamond, S. and E. B. Kinter, "A Rapid Method Utilizing Surface Area Measurements to Predict the Amount of Portland Cement Required for the Stabilization of Plastic Soils," Bulletin 198, Highway Research Board, 1958.

77. Diamond, S. and E. B. Kinter, "Surface Areas of Clay Minerals' as Derived from Measurements of Glycerol Retention," Proceedings, Fifth National Clay Conference, 1956.

78. "Strength Test of Soil-Cement Mixtures," Testing Manual, Texas Highway Department, 1953.

79. Boynton, R. S., Chemistry and Technology of Lime and Limestone, John Wiley and Sons, New York, 1966.

80. Searle, A. B., Limestone and Its Products, Earnest Benn, Ltd. London 1935.

81. Mateos, M. and D. T. Davidson, "Lime Fly Ash Properties in Soil- Lime Stabilization, Bulletin 335, Highway Research Board, 1962.

82. Laguros, J. G., D. T. Davidson, R. L. Hardy and T. Y. Chu, "Evaluation of Lime for Stabill- Ion of Loess," Bulletin 195, Iowa State Experiment Station, 1961.

83. "Lime Testing Procedures," Test Method Tex-600-J, Manual of Testing Procedures, Vol. 3, Texas Highway Department, 1962.

84. "Lime Treatment for Materials in Place," Item 260, Standard Specifi- cations for Road and Bridge Construction, Texas Highway Department, 1961 (also Items 262 and 26A).

85. Thompson, M. R., "Lime Reactivity of Illinois Soils," Journal of the Soil Mechanics and Foundation Engineering Division, Proceedings, ASCE, Vol IXX, No. SMX, September 1966.

86. "Lime Stabilization Construction Manual," Bulletin 326, National Lime Association, 1969.

87. Thompson, M. R., personal conversation.

88. McDowell, Chester, personal conversation.

89. Department of the Army, U.S. Army Engineer School, "Soils Engineering," Section 1, Vol. Ill, Chap. X, October 1967.

90. Eades, J. L. and R. E. Grim, "A Quick Test to Determine Lime Requirements for Lime Stabilization," Highway Research Record No. 139, Highway Research Board, 1966. " ~ " "'*"

268

91. Thompson, M. R., "Lime Treated Soils for Pavement Construction," Journal of the Highway Division, Proceedings, ASCE, Vol. 94, No. HW2, November 1968.

92. Dempsey, B. J. and M. R. Thompson, "Durability Properties of Lime- Soil Mixtures," Highway Research Record No. 235, Highway Research Board, 1968.

93. Department of the Army, "Rigid Airfield Pavements - Airfields Other Than Army," Technical Manual 5-824-3, February 1958.

94. U.S. Army Waterways Experiment Station, Technical Memorandum No. 3-357, "The Unified Soil Classification System," 1953.

95. Department of the Army, Corps of Engineers, "Flexible Pavement Design for Roads, Streets, Walks, and Open Storage Areas," EM 1110-345-291, February 1961.

96. Department of the Army, "Planning, Site Selection and Design of Roads, Airfields and Heliports in the Theater of Operations," Technical Manual IM 5-330, July 1963.

97. Welnert, H. H., "Climate, Engineering Petrology and the Durability of Natural Road Building Materials in Southern Africa,"Rhodeslan Engineer, May 1970.

98. Hudson, W. R., F. N. Finn, B. F. McCullough, K. Nair, and B. A. Vallerga, "Systems Approach to Pavement Design" National Cooperative Highway Research Program, NCHRP Project 1-10, March 1968.

99. Haas, R. C. B. and K. 0. Anderson, "A Design Subsystem for the Response of Flexible Pavements at Low Temperatures," Proceedings, Association of Asphalt Paving Technologists, 1969.

100. Kasianchuk, D. A., "Fatigue Considerations in the Design of Asphalt Concrete Pavements," Thesis, University of California, Berkeley, 1968.

101. Hutchinson, B. G. and R. C. G. Haas, "A Systems Analysis of the Highway Pavement Design Process," Highway Research Record No. 239, Highway Research Board, 1968.

102. Monismlth, C. L., "Some Applications of Theory in the Design of Asphalt Pavements," Fifth Annual Nevada Street and Highway Conference, University of Nevada, 1970. '

103. Haas, R. C. G. and W. A. Phang, "Case Studies of Pavement Shrinkage Cracking as Feedback for a Design Subsystem," presented at HRB meeting, January 1970.

104. Velezis, J. A. and Wayne A. Dunlap, "Development of an Information Retrieval System for Lime Stabilization," report to Air Force Weapons Laboratory (WLDC-TA) , May 1970.

269

■.•■-. ■ in in" IIHIIHIIIIIIIIIIHI mnmmtfrtnrarTr»^.. ..„.„r-^,^-,,-

ACKNOWLEDGMENTS

Recognition of the many advantages of soil stabilization has prompted

considerable research and publication in this field. As might be expected in

an area with such a vast amount of literature, there are often conflicting

statements and opinions. In an effort to clarify as much of this information

as possible and to benefit from the personal experience of experts in the

field of soil stabilization, the authors held personal conferences with many

of these experts. Their knowledge is liberally sprinkled throughout this

report - often without reference to their contributions - and their help is

gratefully acknowledged.

The basic information contained in this report was presented at a Soil

Stabilization Review at Kirtland Air Force Base, New Mexico, on 20-22 July,

1970. The helpful comments of those participating in this review are also

incorporated in this report, insofar as possible.

Those individuals who contributed by allowing personal interviews are

acknowledged below.

Persons Consulted Representing

Producer Groups

Mr. Vaughn Marker Mr. Fred N. Finn Mr. William J. Kari Mr. Loyd D. Coyne Mr. Larry E. Santucci Mr. Conard M. Kelley Mr. Kenneth A. Gutschick Mr. G. F. Robbins Mr. J. 0. Izatt

Asphalt Institute - Berkeley, Calif. Asphalt Institute - Berkeley, Calif. Chevron Asphalt Company Chevron Asphalt Company Chevron Asphalt Company National Lime Association National Lime Association Portland Cement Association Shell Oil Company

270

Consumer Groups

Mr. William A. Garrison Mr. C. R. Foster Mr. Chester McDowell Mr. Robert Long Mr. Charles R. White

Mr. David J. Lambiotte

Mr. David Franklin Mr. Eugene Hanson Mr. R. N. White Mr. Walter K. Kastner

Contra Costa County, California National Asphalt Paving Association Texas Highway Department Texas Highway Department U. S. Naval Civil Engineering

Laboratory U. S. Naval Civil Engineering

Laboratory U. S. Forest Service - Georgia U. S. Forest Service - Utah U. S. Forest Service - California Washington Asphalt Company

Special Interest Groups and Consultants

Dr. R. L. Terrel Dr. Robert P. Lottman Dr. Robert L. Schuster Mr. Carl L. Monismith Mr. Kenneth Line11

Mr. North Smith

Mr. John C. Cook Mr. Milan Krukur Mr. Clyde V. Jones Mr. Spencer J. Buchanan Mr. Oscar A. White

University of Washington University of Idaho University of Idaho University of California U. S. Army Engineers Cold Regions

Research and Engineering Laboratories U. S. Army Engineers Cold Regions

Research and Engineering Laboratories Washington State University Washington State University Consulting Engineer Consulting Engineer Retired - Oregon Highway Department

271 / 272

basis for the development of a soil stabilization … · strength of soil cement mixtures 83 17...

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