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Fly Ash Applicability in Pervious Concrete
Thesis
Presented in Partial Fulfillment of the Requirements for the Degree Master of Science in
the Graduate School of The Ohio State University
By
Na Jin, B. E.
Graduate Program in Civil Engineering
The Ohio State University
2010
Thesis Committee
William E. Wolfe, Advisor
Fabian Hadipriono TanTarunjit Singh Butalia
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2
Copyright by
Na Jin
2010
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ABSTRACT
Pervious concrete has been used in the United State for over 30 years. Because of
its high porosity, the most common usages have been in the area of stormwater
management, but have been limited to use in pavements with low volume traffic because
of its low compressive strength compared to conventional concrete. Fly ash has been
shown in numerous post studies to increase the strength and durability of conventional
concrete. In this study, six batches of pervious concrete with different amounts of
aggregate, cement, and fly ash were prepared to find the mix that generated high
compressive strength and study the effect of fly ash on the compressive strength and
permeability of pervious concrete.
Materials used in this study were selected based on literature reviews and
recommendations from local sources. Unconfined compressive strength tests were carried
out on pervious concrete specimens with fly ash contents of 0%, 2%, 9%, 30%, 32% by
weight of the total cementitious materials. Falling head permeability tests were carried
out on specimens having 2% and 32% fly ash.
The results indicated the pervious concrete containing 2% fly ash can achieve
compressive strength greater than 3,000 psi at void content of 12%, and a compressive
strength 2,300 psi with a permeability of 0.13 cm/s at a void content of 15%. The
pervious concrete with 32% fly ash had a compressive strength of 2,000 psi and the
permeability of 0.21 cm/s at a void content of 15.8%. The failure surfaces of specimens
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with 2% fly ash developed through the coarse aggregates, indicating the high strength of
cement bonds. The failure of specimens containing 32% fly ash was observed to be along
the coarse aggregates surfaces, indicating a lower strength of the paste. Although it was
expected for pervious concrete with 32% fly ash to reach a higher compressive strength at
lower void content, the failure mode indicated that it may not reach the value as high as
that of pervious concrete with 2% fly ash at the same void content.
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DEDICATION
Dedicated to my dear parents and husband.
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ACKNOWLEDGEMENTS
I would like to express my sincere appreciation to my advisor, Dr. William E.
Wolfe, for his guidance, patience, kindness, and encouragement throughout this work. I
would also like to thank Dr. Fabian Hadipriono Tan for his suggestions and endless
support to me during my study. Without their help, the fulfillment of my master degree
would have been impossible.
I would also like to thank Dr. Tarunjit Singh Butalia for his suggestions and help
in facilitating the purchase of experimental equipments in this study. I am also grateful to
all of the professionals for their expertise, support, and kindness: Mr. Mark Pardi, is of
Ohio Concrete, gave me valuable suggestions and guidance on pervious concrete; Mr.
Dan Hunt, is of Buckeye Ready-Mix, carried out one example mix test on pervious
concrete and shared his valuable experience; Mr. Michael Adams, is of Euclid Chemical
Corp., provided with pervious concrete admixtures; Mr. Thomas J. Wissinger, is of the
Olen Corp., provided and delivered coarse aggregates even in bad weather; Mr. Dan Jahn,
is of Anderson Concrete, arranged a visit to the concrete company and provided with
portions of perivous concrete components.
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Table of Contents
ABSTRACTii
DEDICATIONiv
ACKNOWLDEGEMENTS.v
VITA...vi
List of Figures..x
List of Tables........xiii
CHAPTER 1: INSTRODUCTION...............................................................................1
1.1 Background............................................................................................................11.2 Objectives..............................................................................................................2
1.3 Organization ..........................................................................................................3
CHAPTER 2: LITERATURE REVIEW OF PORTLAND CEMENT PERVIOUS
CONCRETE ..................................................................................................................5
2.1 Introduction ...........................................................................................................5
2.2 Benefits and Problems ...........................................................................................62.2.1 Benefits...........................................................................................................6
2.2.2 Problems .........................................................................................................82.3 Components of Pervious Concrete .......................................................................11
2.3.1 Coarse Aggregate..........................................................................................112.3.2 Fine Aggregate..............................................................................................12
2.3.3 Cement..........................................................................................................122.3.4 Fly Ash .........................................................................................................13
2.3.5 Water ............................................................................................................132.3.6 Admixtures ...................................................................................................14
2.4 Important Properties of Pervious Concrete ...........................................................162.4.1 Permeability ..................................................................................................16
2.4.2 Compressive Strength....................................................................................202.4.3 Freeze-thaw Durability..................................................................................21
2.4.4 Modulus of Elasticity ....................................................................................24
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2.5 Factors Affect Compressive Strength and Permeability of Pervious Concrete.......242.5.1 Effect of Void Content ..................................................................................25
2.5.2 Effect of Aggregate.......................................................................................272.5.3 Effect of Aggregate/Cement Material Ratio...................................................28
2.5.4 Effect of Water/Cement Ratio .......................................................................28
2.5.5 Effect of fly ash.............................................................................................292.5.6 Effect of Compaction Energy ........................................................................292.5.7 Effect of Fibers .............................................................................................31
2.5.8 Effect of Other Factors ..................................................................................322.6 Standard Test Methods.........................................................................................33
2.7 Pervious Concrete Design ....................................................................................342.7.1 Pervious Concrete Mix Design ......................................................................34
2.7.2 Pervious Concrete Pavement Hydraulic Design.............................................362.7.3 Pervious Concrete Pavement Structural Design .............................................37
CHAPTER 3: LITERATURE REVIEW OF FLY ASH............................................44
3.1 Introduction of Coal Combustion Products (CCPs) ..............................................44
3.2 Introduction of Fly Ash........................................................................................473.2.1 Properties of Fly Ash.....................................................................................48
3.2.2 Class C and Class F Fly Ash..........................................................................483.2.3 Utilization of Fly Ash in Concrete .................................................................48
3.2.4 Environmental Benefits of Fly Ash Use.........................................................503.3 Effect of Fly Ash on Concrete..............................................................................51
3.3.1 Thermal Cracking .........................................................................................513.3.2 Compressive Strength....................................................................................51
3.3.3 Durability......................................................................................................533.3.4 Permeability ..................................................................................................54
3.3.5 Sulfate Attack ...............................................................................................553.4 Fly Ash in Pervious Concrete...............................................................................56
3.5 Summary .............................................................................................................56
CHAPTER 4: LABORATORY MIX AND TEST .....................................................59
4.1 Introduction .........................................................................................................594.2 Mix Preparation ...................................................................................................59
4.2.1 Mix Materials................................................................................................594.2.2 Mix Design ...................................................................................................65
4.2.3 Mixing Equipment ........................................................................................714.2.4 Specimen Mold .............................................................................................74
4.3 Mixing Procedure ................................................................................................744.4 Compaction Method.............................................................................................75
4.5 Curing Method.....................................................................................................764.6 Laboratory Tests ..................................................................................................77
4.6.1 Unit Weight and Void Content ......................................................................77
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4.6.2 Compressive Strength....................................................................................794.6.3 Permeability ..................................................................................................80
4.7 Summary of Test Procedure.................................................................................83
CHAPTER 5: DISCUSSION ON TEST RESULTS ................................ ..................86
5.1 Introduction .........................................................................................................865.2 Void Content vs. Unit Weight ..............................................................................86
5.3 Effect of Compaction Energy...............................................................................875.4 Effect of W/C Ratio, A/C Ratio and Fly Ash on Void Content .............................90
5.5 Compressive Strength ..........................................................................................905.5.1 Compressive Strength vs. Curing Period........................................................91
5.5.2 Compressive Strength vs. Void Content ........................................................925.5.3 Compressive Strength vs. Unit Weight ..........................................................94
5.5.4 Compressive Stress-strain Curves vs. Void Content.......................................945.5.5 Compressive Failure vs. Curing Period..........................................................98
5.5.6 Failure Modes ...............................................................................................995.6 Permeability.......................................................................................................103
CHAPTER 6: SUMMARY, CONCLUSION, AND RECOMMENDATIONS.......107
6.1 Summary ...........................................................................................................107
6.2 Conclusion.........................................................................................................1096.3 Recommendations for Future Work....................................................................111
REFERENCES..........................................................................................................113
APPENDIX A: EXAMPLES OF PERVIOUS CONCRETEEXPERIMENTS FROM
LITERATURE REVIEWS .......................................................................................121
APPENDIX B: PROPERTIES OF PERVIUOS CONCRETE COMPONENTS ...125
APPENDIX C: LABORATORY TEST RESULT ................................ ................... 137
APPENDIX D: PERVIOUS CONCRETE MIX DESIGN PROGRAM CODE .....168
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List of Figures
Figure 2.1. Model Resulting from the Nonlinear Fitting of the Saturated Hydraulic
Conductivity and Total Porosity Data to the Carman-Kozeny Equation .........................18Figure 2.2. Plot of the Ergun Equation and Values Calculated Using the Falling Head
Experimental Data from Samples Calculated withDp= 0.1,Dp= 0.3, andDp=0.6.(adapted from Montes and Haselbach
).....................................................................19
Figure 2.3. Relationship between Strength, Void Content and Permeability for SeveralTrial Mixes of Portland Cement Pervious Concrete........................................................26
Figure 2.4. Nomograph to Determine Structural Number (Pavement Strength) .............38
Figure 3.1. Uses of Coal Combustion Products in 2008(AACA adapted from U. SEnvironmental Protection Agency (EPA)) .....................................................................45Figure 3.2. 1966-2007 CCP Beneficial Use vs. Production (AACA) ..............................46
Figure 3.3. Coal Combustion Products Generation and Use (Short Tons) (AACA adaptedfrom EPA) .....................................................................................................................47
Figure 3.4. Top Uses of Coal Fly Ash 2003 (AACA adapted from)................................49Figure 3.5. Comparison between Ash Concrete Compressive Strength and Plain Cement
Concrete Compressive Strength. ....................................................................................52Figure 3.6. Effect of Fly Ash on Permeability of Concrete (adapted from) .....................55
Figure 4.1. Grain Distribution Curve of Size Number 8 River Gravel(Olen Corp.)........61Figure 4.2. Pervious Concrete Mix Calculation Program................................................68
Figure 4.3. 20 quart Blakeslee Mixer .............................................................................72Figure 4.4. Specimen Mixed Using 20 Quart Blakeslee Mixer .......................................72
Figure 4.5. 3.4ft3capacity Gilson 39555 (drum speed speed 22 ~ 25 RPM) ...................73
Figure 4.6. INSTRON-5585 Compressive Strength Testing Machine.............................80
Figure 4.7. Falling Head Permeability Test for Pervious Concrete Specimen .................82Figure 4.8. Pervious Concrete Specimen for Permeability Test ......................................82
Figure 5.1. Relationship between Void Content (%) and Unit Weight (lb/ft3).................87Figure 5.2. Void Contents of Specimens Compacted by Different Methods ...................88
Figure 5.3. The Specimen Compacted by Proctor Hammer ............................................89Figure 5.4. Pervious Concrete Mix #3~#6 Compressive Strength vs. Curing Period.......92
Figure 5.5. Relaiton between 28-day Compressive Strength and Void Content ..............93
Figure 5.6. Relationship between 28-day Compressive Strength and Unit Weight..........94Figure 5.7. Stress-strain Curves Tested on Specimens with Different Void Content at 28-day Curing Period, Mix #5.............................................................................................96
Figure 5.8. Stress-strain Curves Tested on Specimens with Different Void Content at 28-day Curing Period, Mix #6.............................................................................................97
Figure 5.9. Stress-strain Curves Tested on Specimens with Void Content 18% at 7-day,21-day, and 28-day Curing Periods, Mix #6 ...................................................................99
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Figure 5.10. Failure Mode I of Pervious Concrete Samples..........................................100Figure 5.11. Failure Mode II of Pervious Concrete Samples.........................................100
Figure 5.12. Failure of Specimen Compacted by Standard Proctor Hammer (Mix #6)..101Figure 5.13. Failure Surface Comparison between Specimen from Mix #5 and Mix #6102
Figure 5.14. Relationship between Void Content and Permeability of Pervious Concrete
Specimens ...................................................................................................................103Figure 5.15. Comparison of Permeability Test Results with Previous Studies ..............106Figure 6.1. Permeability and 28-day Compressive Strength vs. Void Content ..............109
Figure B.1. Properties of Coarse Aggregates................................................................126Figure B.2. Properties of Cement (St. Marys) ..............................................................127
Figure B.3. Properties of High Range Water Reducer (Euclid Chemical Company) .....128Figure B.4. Properties of Mid-Range Water Reducer (Euclid Chemical Company) ......130
Figure B.5. Properties of Mid-Range Water Reducer (Euclid Chemical Company) ......132Figure B.6. Properties of Viscosity Modifying Admixture (Euclid Chemical Company)
....................................................................................................................................134Figure B.7. Properties of Fiber (Euclid Chemical Company)........................................135
Figure C.1. 11-day Compressive Stress-strain Curve of Specimen with Void Contend of31% from Mix #3 ........................................................................................................147
Figure C.2. 21-day Compressive Stress-strain Curve of Specimen with Void Contend of31% from Mix #3 ........................................................................................................147
Figure C.3. 28-day Compressive Stress-strain Curve of Specimen with Void Contend of31% from Mix #3 ........................................................................................................148
Figure C.4. 7-day Compressive Stress-strain Curve of Specimen with Void Contend of27% from Mix #4 ........................................................................................................148
Figure C.5. 21-day Compressive Stress-strain Curve of Specimen with Void Contend of27% from Mix #4 ........................................................................................................149
Figure C.6. 28-day Compressive Stress-strain Curve of Specimen with Void Contend of27% from Mix #4 ........................................................................................................149
Figure C.7. 7-day Compressive Stress-strain Curve of Specimen with Void Contend of12% from Mix #5 ........................................................................................................150
Figure C.8. 21-day Compressive Stress-strain Curve of Specimen with Void Contend of12% from Mix #5 ........................................................................................................150
Figure C.9. 28-day Compressive Stress-strain Curve of Specimen with Void Contend of13% from Mix #5 ........................................................................................................151
Figure C.10. 7-day Compressive Stress-strain Curve of Specimen with Void Contend of17% from Mix #6 ........................................................................................................151
Figure C.11. 21-day Compressive Stress-strain Curve of Specimen with Void Contend of18% from Mix #6 ........................................................................................................152
Figure C.12. 28-day Compressive Stress-strain Curve of Specimen with Void Contend of18% from Mix #6 ........................................................................................................152
Figure C.13. 28-day Compressive Stress-strain Curve of Specimen with Void Contend of16% from Mix #5 ........................................................................................................153
Figure C.14. 28-day Compressive Stress-strain Curve of Specimen with Void Contend of15% from Mix #5 ........................................................................................................153
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Figure C.15. 28-day Compressive Stress-strain Curve of Specimen with Void Contend of12% from Mix #5 ........................................................................................................154
Figure C.16. 28-day Compressive Stress-strain Curve of Specimen with Void Contend of12% from Mix #5 ........................................................................................................154
Figure C.17. 28-day Compressive Stress-strain Curve of Specimen with Void Contend of
14% from Mix #5 ........................................................................................................155Figure C.18. 28-day Compressive Stress-strain Curve of Specimen with Void Contend of14% from Mix #5 ........................................................................................................155
Figure C.19. 28-day Compressive Stress-strain Curve of Specimen with Void Contend of13% from Mix #5 ........................................................................................................156
Figure C.20. 28-day Compressive Stress-strain Curve of Specimen with Void Contend of18% from Mix #6 ........................................................................................................156
Figure C.21. 28-day Compressive Stress-strain Curve of Specimen with Void Contend of20% from Mix #6 ........................................................................................................157
Figure C.22. 28-day Compressive Stress-strain Curve of Specimen with Void Contend of22% from Mix #6 ........................................................................................................157
Figure C.23. 28-day Compressive Stress-strain Curve of Specimen with Void Contend of24% from Mix #6 ........................................................................................................158
Figure C.24. 28-day Compressive Stress-strain Curve of Specimen with Void Contend of24% from Mix #6 ........................................................................................................158
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List of Tables
Table 2.1. NMCRA Classification of Regions and Recommendation of Precautions ofUtilizing pervious concrete ...........................................................................................22
Table 2.2. Compaction Method Conducted by Rizvi et al...............................................31Table 2.3. Recommended Typical Mix Design by National Ready Mixed Concrete
Association....................................................................................................................35Table 2.4. Recommended Typical Mix Design by the Southern California Ready Mix
Concrete Association (adapted from) ............................................................................35Table 2.5. Recommended Typical Mix Design by the Euclid Chemical Company .........35
Table 4.1. Physical Properties of #8 River Gravel (Olen Corp.) .....................................61
Table 4.2. Coarse Aggregate Distribution (Olen Corp.)..................................................61Table 4.3. Chemical Properties of St. Marys Type I Cement (St. Marys, Inc.)................63Table 4.4. Physical Properties of fly ash ........................................................................64
Table 4.5. Admixtures from Euclid Chemical Company ................................................65Table 4.6. Pervious Concrete Mix Design ......................................................................66
Table 4.7. Mix No. Corresponding to Mix ID. ...............................................................67Table 4.8 Compaction Method ID Explanation ..............................................................75
Table 4.9. Pervious Concrete Mixes Compacted Using Different Methods Mix .............76Table 4.10. Specific Gravities of Materials in Portland Cement Pervious Concrete Mix.79
Table A.1: Examples of Laboratory Tests on Pervious Concrete. .................................122Table A.2. Examples of Field Projects of Pervious Concrete........................................124
Table C.1. Mix Design of Pervious Concrete Mix #1 ...................................................138Table C.2. Unit Weight and Void Content of 4in x 8in Samples from Pervious Concrete
Mix #1.........................................................................................................................138Table C.3. Mix Design of Pervious Concrete Mix #2 ...................................................139
Table C.4. Unit Weight and Void Content of 4in x 8in Samples from Pervious ConcreteMix #2.........................................................................................................................139
Table C.5. Mix Design of Pervious Concrete Mix #3 ...................................................140Table C.6. Unit Weight and Void Content of 4in x 8in Samples from Pervious Concrete
Mix #3.........................................................................................................................140Table C.7. Mix Design of Pervious Concrete Mix #4 ...................................................141
Table C.8. Unit Weight and Void Content of 4in x 8in Samples from Pervious Concrete
Mix #4.........................................................................................................................141Table C.9. Mix Design of Pervious Concrete Mix #5 ...................................................142Table C.10. Unit Weight and Void Content of 4in x 8in Samples from Pervious Concrete
Mix #5.........................................................................................................................142Table C.11. Unit Weight and Void Content of 3in x 6in Samples from Pervious Concrete
Mix #5.........................................................................................................................143Table C.12. Mix Design of Pervious Concrete Mix #6 .................................................143
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Table C.13. Unit Weight and Void Content of 4in x 8in Samples from Pervious ConcreteMix #6.........................................................................................................................144
Table C.14. Unit Weight and Void Content of 3in x 6in Samples from Pervious ConcreteMix #6.........................................................................................................................144
Table C.15. Compressive Strength of Specimens from Mix #1~#6 at 7, 21, and 28 Days
Curing Periods.............................................................................................................145Table C.16. 28-day Compressive Strength of Specimens from Mix #1~#6 with VariousVoid Content ...............................................................................................................146
Table C.17. Measured and Calculated Permeability of Pervious Concrete Specimens fromLiterature Review ........................................................................................................159
Table C.18. Permeability Calculation Parameters in Falling Head Permeability Test ...161Table C.19. Permeability Test Data for Specimen with Void Content of 19.5% from Mix
#5 ................................................................................................................................162Table C.20. Permeability Test Data for Specimen with Void Content of 19.5% from Mix
#5 ................................................................................................................................162Table C.21. Permeability Test Data for Specimen with Void Content of 17.0% from Mix
#5 ................................................................................................................................163Table C.22. Permeability Test Data for Specimen with Void Content of 16.0% from Mix
#5 ................................................................................................................................163Table C.23. Permeability Test Data for Specimen with Void Content of 14.9% from Mix
#5 ................................................................................................................................164Table C.24. Permeability Test Data for Specimen with Void Content of 27.2% from Mix
#6 ................................................................................................................................164Table C.25. Permeability Test Data for Specimen with Void Content of 25.0% from Mix
#6 ................................................................................................................................165Table C.26. Permeability Test Data for Specimen with Void Content of 21.0% from Mix
#6 ................................................................................................................................165Table C.27. Permeability Test Data for Specimen with Void Content of 21.5% from Mix
#6 ................................................................................................................................166Table C.28. Permeability Test Data for Specimen with Void Content of 15.8% from Mix
#6 ................................................................................................................................166Table C.29. Void Contents of Specimens Compacted at Different Compaction Methods
....................................................................................................................................167
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CHAPTER 1
INTRODUCTION
1.1 Background
According to National Ready Mixed Concrete Association (NRMCA)1
,
pervious concrete is a special type of concrete with a high porosity used for concrete
flatwork applications that allows water from precipitation and other sources to pass
through it, thereby reducing the runoff from a site and recharging ground water
levels. It is also known as no-fines concrete and is composed of Portland cement,
coarse aggregate, water, admixtures, and little or no sand. In the past 30 years,
pervious concrete has been increasingly used in the United States, and is among the
Best Management Practices (BMPs) recommended by the Environmental Protection
Agency (EPA)2. By capturing stormwater and allowing it to seep into the ground,
pervious concrete is instrumental in recharging groundwater, reducing stormwater
runoff, and meeting U.S. EPA stormwater regulations. Other benefits of using
pervious concrete are: reduction of downstream flows, erosion and sediment;
reduction of large volumes of surface pollution flowing into rivers; decrease of urban
heat island effect; eliminating traffic noise; and enhancing safety of driving during
raining. The use of pervious concrete in building site design can also aid in the
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process of qualifying the building for Leadership in Energy and Environmental
Design (LEED) Green Building Rating System credits2.
Due to the advantages of pervious concrete, the utilization and construction
properties of pervious concrete have been studied by many researchers3,4,5,6. The
characteristic of high permeability of pervious concrete contributes to its advantage in
storm water management. However, the mechanical properties such as compressive
strength are reduced due to this character, limiting the application of pervious
concrete to the roads that have light volume traffic.
The advantage of pervious concrete can be enhanced by substituting some of
the cement with other materials, such as fly ash. Fly ash is one of the by-products of
coal combustion in power generation plants. Large amount of fly ash are discarded
each year, increasing costs for disposal. On the other hand, fly ash has been shown to
improve the overall performance of concrete, when substituted for a portion of the
cement7. Hence, when fly ash is used in pervious concrete, the occupation of landfill
space can be reduced and CO2 emissions generated during cement production can be
decreased, improving the sustainability of pervious concrete.
1.2 Objectives
The objective of this research is to investigate the effects on the important
engineering properties of pervious concrete with the use of fly ash. The physical
properties examined include compressive strength and permeability of pervious
concrete. The parameters that affect the strength and the hydraulic conductivity of
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pervious concrete will be analyzed. The potential use of pervious concrete containing
a large portion of fly ash will also be discussed.
1.3 Organization
This thesis consists of six chapters and four appendices. Chapter 1 is an
introduction of pervious concrete background and the study objectives. Chapter 2
presents literature reviews of pervious concrete, including benefits and problems, mix
designs, and properties of pervious concrete. Chapter 3 contains a brief literature
review of fly ash, introducing the application and effect of fly ash on concrete
properties. Chapter 4 introduces the laboratory mixing and laboratory tests, including
the selection of materials, mixing equipment, mix design, compaction method, and
test equipments. Chapter 5 elaborates on the test results, including void content,
compressive strength, and permeability of pervious concrete specimens. Chapter 6
summarizes the conclusions of the study, discusses the applicability of pervious
concrete that contains large amounts of fly ash, and provides with recommendations
for future work. Appendix A presents examples of pervious concrete experiments
taken from literature reviews. Appendix B illustrates the properties of pervious
concrete components used in this research. Appendix C presents the laboratory test
results. Appendix D shows codes of a program developed for pervious concrete mix
design.
1NRMCA CIP 38 pervious concrete brochure of National Ready Mixed
Concrete Association (NRMCA),
(Feb. 01, 2010).
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2National Ready Mixed Concrete Association (NRMCA),
(May 24, 2010).
3
Offenberg, M. (2008). Is pervious concrete ready for structural applications?Structure Magazine, February,p. 48.
4Johnston, K. (2009). Pervious concrete: past, present and future. Green
Building, Concrete Contractor,
(April. 24, 2010).
5Schaefer, V. R., Suleiman, M. T., Wang, K., Kevern, J. T., and Wiegand, P.
(2006). An overview of pervious concrete applications in stormwatermanagement and pavement systems. < http://www.rmc-
foundation.org/images/PCRC%20Files/Hydrological%20&%20Environmental%20Design/An%20Overview%20of%20Pervious%20Concrete%20Applications%20
in%20Stormwater%20Management%20and%20Pavement%20Systems.pdf> (Jun.16, 2010).
6Yang, J., and Jiang. G. (2003). Experimental study on properties of pervious
concrete pavement materials. Cement and Concrete Research, vol. 33, pp. 381-386.
7Headwaters Resources (2005). Fly ash in pervious concrete. Bulletin No. 29,
(May 21, 2010).
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CHAPTER 2
LITERATURE REVIEW OF PORTLAND CEMENT PERVIOUS CONCRETE
2.1 Introduction
Offenberg3stated that the first popular usage of pervious concrete was in post-
World War II England where it was used in two-story homes known as the Wimpey
Houses. During World War II, nearly two third of Britains houses had been
destroyed; and no new buildings had been constructed since 1939. Consequently, the
demand for housing was very high, causing a shortage of bricks. In this situation,
people were seeking alternate construction materials that were economical, reliable
and efficient. No-fine concrete was then used in some parts of the walls by Wimpey 8
architects and engineers to decrease the cost.
In the United States, pervious concrete has been used for almost 30 years
since it was first introduced in California4. In order to study the factors influencing
the performance of pervious concrete, researchers have conducted experiments varing
mix proportions of cement, water, coarse aggregate, sand, fly ash, and admixtures.
According to experimental studies6,7,9,10,11,12,13
, researchers have found that factors
that affect the mechanical properties of pervious concrete are void content, aggregate
to cement ratio, fine aggregate amount, coarse aggregate size, coarse aggregate type,
compaction energy, and curing period.
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2.2 Benefits and Problems
Due to the absence of fine aggregate, pervious concrete has high porosity,
which brings both benefits and drawbacks to construction.
2.2.1 Benefits
Since the pervious concrete pavement is permeable, water can be captured and
flow through the pavement during rainfall. In the mean time, free air is stored in the
pavement and allows the communication between the subsurface and the air. These
properties offer many advantages for pervious concrete.
2.2.1.1 Storm-water Management
One of the primary uses of pervious concrete is in storm water management.
Due to its high porosity, pervious concrete can capture stormwater and provide a path
for water to flow into the subsoil, helping to naturally adjust the ground water level.
Furthermore, instead of being carried into rivers and lakes by rain water, the residues
on pavement roads will be absorbed by pervious concrete or underneath soils, and
then degraded by microorganisms in soils2. Consequently, the pollution of water
resources could be decreased substantially, dramatically saving expense of storm
water management.
2.2.1.2 Heat Island Effect
Pervious concrete is much cooler than asphalt and conventional concrete. First
of all, the light color reflects more ultraviolet rays from sun and absorbs less heat than
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asphalt. Secondly, the voids in pervious concrete allow it to store less heat than
conventional concrete does. This character benefits the districts in hot weather
climates. For instances, the group of National Center of Excellence for Sustainable
Materials and Renewable Technology at Arizona State University recommended the
utilization of pervious concrete for minimizing the urban heat-island effect14
. Houston
Advanced Research Center (HARC)15
published a report titled Cool Houston! A
Plan for Cooling the Region, in which the benefits of reducing heat island effect in
high density urban areas by using pervious concrete has been introduced.
2.2.1.3 Traffic Benefits
Pervious concrete shows several advantages on traffic. Firstly, the large
amounts of voids in pervious concrete are beneficial to reducing traffic noise. As
stated by Kim and Lee16
, pervious concrete is applied for sound barriers or
pavements to absorb traffic (tire) noise and reduce sound wave reflection. To
investigate this property of absorption, Kim and Lee16
created a model to study the
acoustic absorption ability of pervious concrete, considering the gradation and shape
of aggregates and void content on pervious concrete pavement. The results calculated
by the modeling were compared with experimental and statistical results from
previous studies. All results illustrated that the maximum acoustic absorption ability
was increased with void content and was hardly affected by the shape of aggregate
when pervious concrete was compacted well. Secondly, pervious concrete enhances
the safety of driving during raining because of the elimination of ponding.
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2.2.1.4 LEED
The usage of pervious concrete in building site design can also aid in the
process of qualifying for Leadership in Energy and Environmental Design (LEED)
Green Building Rating System credits. LEED was developed by the U.S. Green
Building Concil (USGBC). It provides a concise framework for identifying and
implementing practical and measurable green building design, and construction.
LEED for New Construction and Major Renovations version 2.2 has maximum total
of 69 points, in which concrete can earn up to 25 points. In addition, with the usage of
fly ash or other recycled materials in pervious concrete, up to 5 more credits could be
earned2.
2.2.2 Problems
High porosity is the necessary condition that makes pervious concrete
permeable, and is the main beneficial characteristic of pervious concrete. However it
can cause problems that limit the utilization of pervious concrete.
2.2.2.1 Compressive Strength
The bearing capacity of pervious concrete is decreased because of the
existence of large amounts of air voids. The low strength limits the utilization of
pervious concrete to parking-lots, side walks, and other low-volume traffic roadways.
Obviously, high porosity and strength are two incompatible features of pervious
concrete. This disadvantage initiates the study on pervious concrete aim to improve
its compressive strength while maintaining the relative high porosity.
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2.2.2.2 Freeze-thaw Durability
The usage of pervious concrete in a freeze-thaw environment is also a concern,
especially in the northern area of the United States, which are districts experiencing
cold weather. The pervious concrete is more vulnerable to be destroyed under freeze-
thaw weather. Research has been done to study the suitability of pervious concrete in
this type of climate. Regulations have been made to ensure the applicability of the
pervious concrete. For example ASTM C 666M-0317
Standard Test Method for
Resistance of Concrete to Rapid Freezing and Thawing specifies the standard test
method to determine the resistance of concrete specimens to rapidly repeated cycles
of freezing and thawing in the laboratory following procedure A,Rapid Freezing and
Thawing in Water, and procedure B,Rapid Freezing in Air and Thawing in Water.
2.2.2.3 Abrasion
Abrasion of pervious concrete may limit its utilization. Raveling may happen
if aggregate is not sufficiently coated with cement paste. Other factors such as low
Water/Cement (W/C) ratio, dry weather, especially the rough surface also make
aggregate vulnerable to the abrasion. Theoretically, the abrasion of surface may make
surface more uneven and worsen abrasion over time. However, Hein and Schindler18
studied field projects constructed on the Auburn University campus, and found that
after curing of pervious concrete, about only 10% of surface aggregates were
displaced. But remaining surface was smooth enough as for a sidewalk and had
performed very well for three years.
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2.2.2.4 Clogging Maintenance
Clogging is an unavoidable problem due to the existence of voids in pervious
concrete. The open voids are highly prone to be clogged during the utilization of
pervious concrete pavement over time. The U. S. EPA recommends that cleaning
need to be done regularly to prevent clogging2. Two methods of cleaning are
currently used: vacuum sweeping and high pressure washing. Even though cleaning is
performed regularly, not all contaminants are removed and the performance of
pervious concrete may lessen over the years. Moreover, the residues may cause
contamination of the water that runs through the pervious concrete. Hence,
stormwater testing is recommended in critical situations to preserve the quality of
ground water and inspect the permeability of pervious concrete.
2.2.2.5 Cost
Typically, the initial cost of pervious concrete is greater than that of
conventional concrete. However, because the lifespan of pervious concrete is longer
than that of the regular concrete2, some of the added cost is offset. The high initial
cost of pervious concrete is partly caused by the construction of the subgrade. A thick
layer of open gravel subgrade is usually installed under the pavement to provide the
storage and drainage of water. With such subgrade, pervious concrete normally can
perform very well even when built on clay soils. An example is presented by Dietz19
,
who tested a subgrade of 10-in. thick layer of open graded gravel with undrained
system below. The subgrade showed good storage and drainage conditions. In general,
a thick layer of coarse aggregate provides greater storage capacity and a longer time
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allows water to exfiltrate to the native soils before underdarin flow would begin19
.
But the construction of subgrade increases the total cost of the pervious concrete
pavement. Another reason is the increased maintenance cost for pervious concrete
pavement after construction. As stated before, clogging problems need to be solved to
ensure the serviceability of pervious concrete.
2.3 Components of Pervious Concrete
Pervious concrete is mainly composed by coarse aggregate, cement, and water.
Small amount of fine aggregate may be added to obtain higher compressive strength.
Other admixtures such as High/Middle Range Water Reducer (HRWR, MRWR),
water retarder, viscosity modifying admixtures, and fibers are usually used. In some
cases, fly ash is used as a substitute for Portland cement to enhance the environmental
friendliness of pervious concrete.
2.3.1 Coarse Aggregate
Coarse aggregate is the main component of pervious concrete. The gradation,
size, and type of coarse aggregate have been found to affect the character of pervious
concrete6,9,10,11. In practice, river gravels that have size number of 8 (ASTM C 33 20)
are widely used in construction. Other sizes of river gravels and limestone have been
used in laboratory tests to study the effect of coarse aggregate11
.
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2.3.2 Fine Aggregate
A fine aggregate is sometimes used in pervious concrete to improve the
mechanical capabilities of pervious concrete. On the other hand, the permeability will
typically decrease when fine aggregate is added. Wang et al.10
studied pervious
concrete with a fine aggregate amount of 7% of total aggregate by weight. Wangs
tests illustrated that the compressive strength and freeze-thaw ability of pervious
concrete were significantly improved with addition of fine aggregate while
maintaining adequate water permeability. However, the amount of fine aggregate is
recommended to be limited within 7% of the total aggregate by weight so that
permeability is satisfied10
.
According to the ASTM C 3320
, the fine aggregate shall consist of natural or,
subject to approval, other inert materials with similar characteristics, or combinations
having hard, strong, durable particles. The amount substances such as clay lumps coal
and lignite, shale, and other deleterious substance should be limited within a range
individually, and the total amount should be less than 2% by dry weight. Soundness
loss should be less than 10% by weight. The fine aggregate should be free from
organic impurities.
2.3.3 Cement
Portland cement is another main component of pervious concrete. Type I/II
cement is normally used in pervious concrete9,10,11,12
. The content of cement is
dependent on the amount and size of coarse aggregate and the water content. Various
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amounts of cement are recommended by different agencies and will be introduced in
section 2.7.1.
2.3.4 Fly Ash
Fly ash can be used in pervious concrete as a substitute for a portion of the
cement. Two types of fly ash which are Class C and Class F fly ash are both able to
used in pervious concrete. Currently, fly ash can replace 5-65% of the Portland
cement2 in conventional concrete. However, according to the publication from
Headwaters Resources7
, California Ready Mix Concrete Association (SCRMC)
recommended amount of ASTM C-618 fly ash is only 50-116lb/yd3
in pervious
concrete. The advantage of using fly ash is obvious: fly ash is a by-product of coal
burning in power plants, its utilization saves the energy required to produce the
cement. In addition, fly ash improves the flowability and workability of concrete.
2.3.5 Water
Water is a crucial component in pervious concrete. Wanielista and Chopra11
discussed the importance of adding appropriate amount of water in pervious concrete
mix. Enough water should be added so that cement hydration is thoroughly developed.
However, too much water will settle the paste at the base of the pavement and clog
the pores. Meanwhile, too much water increases the distance between particles,
causing higher porosity and lower strength. Wanielista and Chopra11
stated that the
correct amount of water will maximize the strength without compromising the
permeability characteristics of the pervious concrete.
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2.3.6 Admixtures
Admixtures are sometime necessary for pervious concrete to obtain good
properties. Typical admixtures used in pervious concrete include HRWR, MRWR,
water retarder, viscosity modifying admixtures, air-entraining and fibers. The
admixtures should follow standards of ASTM C 49421
(chemical admixtures) and
ASTM C 26022(Air-entraining admixtures).
2.3.6.1 High/Middle Range Water Reducer
Based on experimental results, less water is used in pervious concrete than in
regular concrete2,9,18
. One of the reasons is too much water causes settlement of
cement at the bottom resulting in clogging. To decrease the water content, a HRWR
or MRWR is often used. The dosages of water reducer used in pervious concrete are
various and should closely follow manufacturers recommendation.
2.3.6.2 Water Retarder
The National Ready Mixed Concrete Association reports that because of the
rapid setting time associated with pervious concrete, retarders or hydration-stabilizing
admixtures are commonly used2. Water retarder can extend setting time so that the
hydration of cement is fully developed.
2.3.6.3 Viscosity Modifying Admixtures
Compared to regular concrete, pervious concrete is very dry and hard to cast.
However with the usage of viscosity modifying admixtures, the workability can be
highly improved, and pervious concrete can be more manageable18. In a field project,
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Hein and Schindler18
found that The use of water reducing admixtures in
combination with viscosity modifying admixtures significantly reduced or eliminated
most of the previous difficulties experienced placing pervious concrete pavements.
Since the usage of viscosity eliminated hard physical labor and improved the
smoothness and quality of pavement, Hein and Schindler claimed it as a major
milestone in facilitating successful placement of quality pervious concrete
pavements.
2.3.6.4 Air-entraining Admixtures
Air-entraining admixtures can be used in pervious concrete to improve its
freeze-thaw durability. Air-entraining admixtures can produce micro-closed air holes,
which can flexibly respond to the forces generated by freeze-thaw cycles. These
micro air bubbles are different from the voids in pervious concrete, which are open
holes and do not functional to sustain freeze-thaw forces.
2.3.6.5 Fibers
Fibers can be used in pervious concrete if higher compressive strength is
required. Experiments by Schaefer et al.23showed that adding latex fibers increases
strength of pervious concrete; Yang and Jiang6used organic polymer fibers and found
that they enhanced the strength of pervious concrete greatly. However, they typically
also cause a decrease in hydraulic conductivity.
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2.4 Important Properties of Pervious Concrete
Permeability, compressive strength, freeze-thaw durability are important
properties of pervious concrete. They are affected by many factors such as water
content, void content, aggregate gradations, W/C ratio, and A/C ratio. Research has
been carried out to study the effect of different factors. In this research W/C ratio
stands for Water/total Cementitious Material ratio for simplification. A/C ratio stands
for total Aggregate/total Cementitious Materials ratio.
2.4.1 Permeability
High permeability is the primary characteristic of pervious concrete. Based on
previous studies24,25,26,27
two permeability tests, the falling head tests and constant
head tests were both used to measure the hydraulic conductivity of pervious concrete
samples taken from sites or made in labs. Some lab testing also simulated the
conditions of pervious concrete in actual applications. Experimental and field tests
found that the typical permeability is larger than 0.1cm/sec or 140in/hour10
, which is
considered as the lower limit of pervious concrete permeability.
McCain and Dewoolkar26
published a study on pervious concrete, in which
falling head permeability tests were carried out on three sets of specimens with
diameter 3 inches, 4 inches, and 6 inches, respectively. The falling head permeability
tests also simulated the situation of winter surface, which was covered by sand-salt
mixture. The results showed that the hydraulic conductivity ranged from 0.68cm/s to
0.98cm/s. One significant and special contribution of this article was the study on the
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decrease of permeability by simulating the winter surface. The results illustrated 15%
average reduction on hydraulic conductivity. However, the permeability was still in
the allowable range (greater than 0.1cm/s).
Crouch et al.27 used a triaxial flexible-wall constant head permeameter to
measure the permeability of pervious concrete in the range of 1 to 14,000 inches/hour
(0.001 to 10 cm/sec). Crouch et al. found the constant head permeability was a
function of three factors: effective air void content, effective void size, and drain
down, where drain down is a result of too much paste for the applied compactive
effort or the paste being too fluid, sealing the lower surface of pervious concrete
sample27
.
Montes and Haselbach25
compared the hydraulic conductivity of pervious
concrete samples taken from three different field-placed slabs using a falling head
permeameter system. To investigate the factors affecting permeability of pervious
concrete, samples were collected with different W/C ratios and A/C ratios. Based on
previous studies7,24,25,26, the average porosity of the samples range from 15% to 30%
is typical for pervious concrete. The results indicated that the hydraulic conductivity
is dependent on the porosity. By comparing experimental results with the calculated
values from the equation, Montes and Haselbach25
studied the relationship between
porosity and hydraulic conductivity and found most fitted value of =17.9 2.3
(Figure 2.1) in the Carman-Kozeny equation: ks = [p3/(1-p)
2], where: ks = the
saturated hydraulic conductivity, p = porosity of pervious concrete (adapted from
Montes and Haselbach25). The effect of cementitious material and the non-spherical
shape of particles had been considered in this equation.
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Figure 2.1. Model Resulting from the Nonlinear Fitting of the Saturated HydraulicConductivity and Total Porosity Data to the Carman-Kozeny Equation
25
Montes and Haselbach25
used the Ergun equation to analyze the flow
condition inside the pervious concrete samples. The Ergun equation has the form: f =
150/Re+ 7/4, where f is a dimensionless friction factor, Re is a modified Reynolds
number which indicates the particular fluid porous media flow situation. The results
of Ergun model calculation presented for pervious concrete samples with various
porosities and saturated hydraulic conductivities were presented by Montes and
Haselbach25(Figure 2.1). The trial results indicated that most of the samples were in
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19
the laminar flow region. However, the flow regime may fall into the transition region
for higher porosity samples impacted by higher hydraulic head25
.
Figure 2.2. Plot of the Ergun Equation and Values Calculated Using the Falling HeadExperimental Data from Samples Calculated with Dp = 0.1, Dp = 0.3, and Dp =
0.6.(adapted from Montes and Haselbach25
)Note: Dp=0.1, 0.3, and 0.6cm can be interpreted as particles with different average
diameters and sphericities so that Dp would be equal to 0.1, 0.3, or 0.6 cm.
Montes and Haselbach25
established the equation between hydraulic
conductivity and porosity of pervious concrete sample as kS= 18 p3
/ (1-p)2
, which
show a high coefficient value between experiment and calculated results. However,
they also claimed the validation of the equation was for the pervious concrete samples
in that specific study, in which the size of aggregate was 3/8 inches ~ 5/8 inches, and
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20
the porosity ranged from 15% to 32%. Although the application of equation is limited,
the study showed the flow regime in pervious concrete is in the laminar flow region,
in which Darcys law can be applied. This study is significant because it verified the
validation of Darcys law, which is assumed to be valid in most study of pervious
concrete permeability.
All articles stated above considered the permeability of pervious concrete in
freshly cast condition. Researchers rarely discussed the performance of pervious
concrete that had been used for a while or had become partially clogged. Haselbach et
al.
24
studied the permeability of pervious concrete in partially clogged condition.
Considering the in-situ pervious concrete pavement, clogging is one of the important
concerns because it will decrease the porosity of pervious concrete, decreasing
permeability. In order to study the effect of clogging, Haselbach et al.24
started with
predicting the permeability of pervious concrete with formulas based on empirical
statistics and theoretical analysis. Then experiments were conducted to simulate the
rainfall and clogging situation, and the results were used to compare with predicted
values. The comparison showed good agreement between experimental results and
calculated values, verifying the validity of the prediction. The specialty of this
research is that it proposed models to predict the permeability of pervious concrete
under the worst condition of clogging, which is usually ignored in most research.
2.4.2 Compressive Strength
According to ASTM C 3928
, a minimum compressive strength of 300psi is
required for pervious concrete. According to field and laboratory tests, pervious
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21
concrete compressive strength regularly falls in a range of 400psi ~ 4,000psi (2.8MPa
~ 28MPa). But the common strength is from 600psi to 1,500psi (4MPa to 10MPa).
Laboratory studies have found compressive strength ranges from 600 psi to 3,600 psi
(4 MPa to 25 MPa)9,10,11.
Wanielista and Chopra11
summarized previous studies on compressive
strength of pervious concrete and stated that researchers agreed that factors affect
pervious concrete compressive strength included: A/C ratio, W/C ratio, coarse
aggregate size, compaction, and curing. Researchers disagree as to whether pervious
concrete can consistently attain compressive strengths equal to conventional
concrete.
2.4.3 Freeze-thaw Durability
Freeze-thaw durability is a crucial property to evaluate the suitability of
pervious concrete in cold weather. Freeze-thaw deterioration happens when concrete
is more than 91% saturated, which is generally true for concrete surfaces. When water
freezes, its volume will increase. The expansion of volume generates large pressures,
which act on concrete. When the pressure is in excess of the tensile strength of
concrete or mortar layer at a surface, cracking and scaling will occur.
Although some field projects indicated that pervious concrete performed well
in freeze-thaw situations, it must be used carefully in cold weather regions. The
NRMCA29
recommends the utilization of pervious concrete in different areas that
have various weather conditions. Table 2.1 shows the classification of different
districts and the suitability of using pervious concrete:
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a thick layer of 8 to 24 inches (200 to 600mm) of open graded stone base, saturation
can be effectively avoided23
.
In order to test the freeze-thaw resistance of pervious concrete, some
researchers did tests on saturated pervious concrete following procedure A, Rapid
Freezing and Thawing in Waterof ASTM C 66617
, requiring less than 5% mass loss
after 300 freeze-thaw cycles10
. However, the fully saturated condition in procedure A
is very severe and not representative of field conditions29
. Theoretically, partially
saturated pervious concrete performs well in freeze thaw region because the voids in
concrete can provide sufficient space for water to move. However, a fully saturated
condition may exist; and pervious concrete should be avoided in regions where this
situation is most likely to happen.
Schaefer et al.23
stated the failure mechanism of pervious concrete when
subjected to freeze-thaw cycles is either a result of aggregate deterioration or cement
paste matrix failure. Aggregate failure is seen by the deterioration or splitting of the
aggregate where a portion (usually 15%) of an aggregate particle becomes separated
from the concrete. Cement paste failure is observed by the raveling of entire pieces of
aggregate from the concrete. According to the experimental results presented by
Schaefer et al., in general, mixes containing limestone (i.e. Mix 3/8-LS) failed by the
deterioration of the aggregate; however, mixes containing the smaller size No. 4 river
gravel failed due to aggregate deterioration and splitting23
.
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24
2.4.4 Modulus of Elasticity
Dynamic modulus of elasticity is another important mechanical characteristic
of pervious concrete. The elastic modulus shows the resistance performance of
pervious concrete to fatigue, and is significant for evaluating the durability of
pavements, which is one of the most important indices to evaluate the pervious-
concrete lifespan.
Crouch et al.9 tested the static moduli of four different pervious concrete
mixes with various aggregate sizes and gradations. The results showed that the static
elastic modulus was inversely proportional to the void content. And the optimum void
range which is from 23% to 31% happened in the mix with uniform gradation.
Crouch et al.9 found that the static elastic modulus decreased with increasing
aggregate and decreasing paste. No effect of aggregate sizes on static elastic modulus
has been shown.
2.5 Factors Affect Compressive Strength and Permeability of
Pervious Concrete
The compressive strength and permeability of pervious concrete have been
investigated and their relationships to void content were found. Higher void content
usually leads to higher permeability and lower compressive strength. Other factors
have also been found through experiments. These factors include aggregate, W/C
ratio, A/C ratio, fly ash, compaction energy9,23,27
.
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2.5.1 Effect of Void Content
Schaefer et al.23
studied effects of different proportions of mixture on the
properties of pervious concrete, and provided results to show the relationship between
strength, void content and permeability for several trial mixes of pervious concrete.
The experimental results showed that the permeability increased and compressive
strength decreased with increasing void content. The relationship is illustrated in
Figure 2.3. As shown, when the void content increased from 15% to 32%, the 7-day
compressive strength of pervious concrete decreased from 3,200psi to 1,300psi, while
the permeability increases from 50in/hour to 2,000in/hour. As can be seen in the
figure, the effect of void content on the measured permeability increased when the
void content increased from about 25% to 32%. Their tests showed that the increase
of permeability became more apparent when the void content was relatively large,
while the compressive strength as a function of void content remains linear.
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Figure 2.3. Relationship between Strength, Void Content and Permeability for
Several Trial Mixes of Portland Cement Pervious Concrete23
Crouch et al.27 also studied the correlation between void content and
permeability in both laboratory and field cored specimens. The results showed
agreement with those from Schaefer et al.23
. The average values illustrated high
strength of bond between void content and permeability with correlation coefficient
0.9737. In addition by comparing the laboratory results with experimental results
from prior studies, Crouch et al.27 found that the permeability at low void content
showed high consistency with the previous experimental results30,31
than those at high
void content. This indicated compressive strength values might be more consistent at
low void content.
Void content has been found as the primary factor that determines the
properties of pervious concrete. It was found to be determined from the concrete mix,
including amount of aggregate, cementitious materials, and water2.
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2.5.2 Effect of Aggregate
The effect of aggregate on compressive strength and permeability of pervious
concrete comes from the coarse aggregate size, type, gradation, and the percentage of
fine aggregate.
2.5.2.1 Effect of Coarse Aggregate Type, Size and Gradation
Mulligan32
stated that since cement bond is limited in pervious concrete and
the aggregate rely on the contact surfaces between one another, the aggregate with
higher stiffness such as granite or quartz would have higher compressive strength
than a softer aggregate such as limestone.
Besides the effect of aggregate type, the size of aggregate is another important
factor for compressive strength and permeability of pervious concrete. Yang and
Jiang6 conducted experiments on pervious concrete mixes having various aggregate
sizes. The results showed that the compressive strength was improved by decreasing
the aggregate size. Yang and Jiang analyzed that the reason that smaller aggregate
size generated higher compressive strength might because it enlarged the bond area
between aggregates. However, decreasing aggregate size also resulted in a decreasing
in the permeability.
The gradation of aggregate also affects the properties of pervious concrete.
Crouch et al.9
found that a more uniform gradation deduced to slightly higher
effective void content. Furthermore, the compressive strength was higher at the same
void content in mix that having uniform gradation. The effect of gradation on
compressive strength and permeability was also studied by Wang et al.10. They
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0.22 and 0.27, and suggested using the lower value, if workability could be
maintained. In contrast, in an actual applicaiton published by NRMCA29
W/C ratio up
to 0.55 was used.
W/C should be large enough so that hydration of cementitious materials can
fully develop. Yang and Jiang6pointed out that the cement bond should provide good
connection between aggregate so that the failure is by splitting of the aggregate, in
which way the mixture most effectively works. However, too much water may
decrease the strength, which is known to be the case in conventional concrete.
Furthermore, excessive water will result in settlement of paste, sealing the bottom of
pervious concrete.
2.5.5 Effect of fly ash
Generally, fly ash is realized to be able to decrease the permeability of
conventional concrete, increase freeze-thaw durability of concrete, and improve the
later-age strength of concrete. The effect of fly ash will be thoroughly discussed in
Chapter 3.
2.5.6 Effect of Compaction Energy
Compaction energy has been shown by several researchers12,13,23,27
to affect
the compressive strength, freeze-thaw durability, and permeability.
Suleiman et al.12
found the significant effect of compaction energy on freeze-
thaw durability and compaction failure mode of pervious concrete based on the
experiments conducted by Schaefer et al.23
. The specimens compacted at lower
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energy sustained less cycles of freeze-thaw (110 cycles) at failure than those (failed at
153 cycles and 196 cycles) compacted at higher energy. Suleiman et al.23
also found
an interesting phenomenon that samples compacted at regular compaction energy
failed through the aggregate, while samples compacted at lower energy failed through
both aggregate and paste.
Crouch et al.27
studied the effect of compaction energy on permeability by
comparing the experimental results of specimens with the same mixture design while
compacted at six different compaction efforts. By investigating the effective air void
content and the permeability of both in field and laboratory pervious concrete
mixtures, Crouch et al. found that larger compaction effort resulted in less effective
void content of pervious concrete.
To further study the effect of compaction energy, various compaction methods
were used and compared by Rizvi et al.13
. The compaction method is determined
from the compaction equipment, compaction cycles, and compaction forces. Widely
used compaction equipment includes standard tamping rod, standard Proctor hammer
in laboratory and compact roller in field.
In the research reported by Rizvi et al.13
, five different consolidation
techniques as illustrated in Table 2.2were used to cast identical 6in x 12in cylinders.
For each consolidation technique, samples were prepared for 7, 14 and 28 day
compressive strength testing, permeability, and air void testing. The results revealed
the optimum compaction technique was a standard Proctor hammer 10times/layer for
2 layers. Samples compacted by this method achieve both relatively high compressive
strength and high permeability. In addition, the cylinders compacted by this method
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also achieved the most consistent results with the least variance for compressive
strength and relatively low standard deviations for permeability and air void13
.
Method Layers
Drops
/Tamping
rod/layer
Voids
(%)
28Days
Compressive
Strength (MPa)
Permeability
(cm/s)
Rod 3 25 18.5 18.3 0.719
Rod 3 15 21.2 21 1.03
Rod 3 5 21.8 15.7 1.027
ProctorHammer
2 10 19.9 17.5 0.584
Proctor
Hammer 2 20 17.2 20.7 1.041Table 2.2. Compaction Method Conducted by Rizvi et al.
13
Compared to the lab testing, the field compaction methods have been less
studied. However, Hein and Schindler18
, when reviewing the projects on Auburn
University campus, mentioned the different compaction results of using vibrating
roller and hand roller in field. By observing these field projects, he stated that
vibrating roller appeared to seal the surface and collapse the pores, providing too
great a compactive effort. The hand roller guided by side forms seemed to provide the
smoothest finish.
2.5.7 Effect of Fibers
The positive effect of fibers has been shown in many studies. Yang and Jiang6
added polymer fibers into the pervious concrete and obtained increased compressive
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strength. The increase of compressive strength might because the fiber enhanced the
binder6. In addition, the permeability was unaffected, which differed to the effects of
other factors and therefore enhanced the advantage of adding fibers in pervious
concrete.
2.5.8 Effect of Other Factors
Some factors such as specimen size and testing method have also been studied
in a few cases. Although these factors are not critical to determine pervious concrete
properties, they were discussed and may be considered in some situations.
The size of specimen is not usually considered because they are generally
compacted to the standard size defined by national codes. For example, 4in x 8in
cylinders are normally used in the United States for compressive strength test; 6in x
12in cylinders were cast in the University of Waterloo in Canada, while rectangular
cylinders were used in China. To study the impact of diameter on cylinder samples,
McCain and Dewoolkar26tested the compressive strength on three sets of specimens
with diameter of 3 inches, 4 inches, and 6 inches. For each set, three identical
specimens were tested. The compressive strength drawn from these experiments
ranged between 650psi (4.5MPa) and 1,100psi (7.6MPa). Even for specimens that
were the same size, the compressive strengths were different with 150 to 260psi. The
experimental results showed that the effect of specimen size was unpredictable.
However, the specimens with 4 inches diameters showed higher average compressive
strength compared to the 3 inches and 6 inches diameters specimens. However, the
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effect of specimen size could not be distinguished from the effect of inconsistent
casting of specimens due to the limited experimental results.
Another factor that affects the compressive strength of pervious concrete is
capping. Capping is sometimes used in compressive strength test to smooth the
surface of pervious concrete specimen, reducing the effect of stress concentration
consequently. The studies on pervious concrete conducted by Kevern33
showed that
the specimens with sulfur capping compound has higher compressive strength than
those without capping.
2.6 Standard Test Methods
Some tests methods that are required for regular concrete may be unnecessary
for pervious concrete. For example, since pervious concrete has low water content
and lower fluidity, the slump test is not informative.
Currently, standard test methods for field permeability, compressive strength,
hardened concrete density and porosity, and flexural strength of pervious concrete are
under development by ASTM C 09/4934
. Only ASTM C 1688 with title of Fresh
concrete Density (Unit Weight) and Void Contenthas been published35
. Obviously,
the progress of developing standard test methods for pervious concrete is only at
beginning. No standard ASTM test procedure has been suggested to measure the
entrained air content for pervious concrete. In fact, before the finalization of
testing/mixing methods for pervious concrete, people are using those designed for
conventional concrete, even those methods may not be appropriate in many situations.
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2.7 Pervious Concrete Design
This section introduces pervious concrete mix design, pervious concrete
pavement structure and hydraulic design. The mix design of pervious concrete is
concerned with the properties of pervious concrete used in the pavement; while the
pervious concrete pavement design is the process of designing the whole system of
pavement including the pavement surface and the subgrade layer.
2.7.1 Pervious Concrete Mix Design
Pervious concrete mix design should generate batches that satisfy compressive
strength and permeability requirements. Typical mix designs of pervious concrete
have been recommended by different agencies such as National Ready Mixed
concrete Association, the Southern California Ready Mix concrete Association, and
the Euclid Chemical Company. The recommended mix designs are shown in Table
2.3, Table 2.4, and Table 2.5. The examples of mix design in laboratory experiments
and in field projects have been done and are listed in Appendix I.
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Material Amount
(pcy)
Cementitious Materials 450 700 lbs
Aggregate 2000 2500 lbs
W/C by Mass 0.27 0.34
A/C by Mass 4 4.5 : 1
Table 2.3. Recommended Typical Mix Design by National Ready Mixed Concrete
Association36
Material Amount (pcy)
Compacted Voids 10%
Cement 580lbs
ASTM C-618 fly ash 50 116 lbs
Total Cementitious Materials 630 696 lbs
Aggregate 27 ft3
Table 2.4. Recommended Typical Mix Design by the Southern California Ready MixConcrete Association (adapted from
1)
Material Amount (pcy)
Cement 600lbs
Coarse Aggregate 3/8 Limestone 2600 lbs
Water 160 lbs
W/C by Mass 0.27
Table 2.5. Recommended Typical Mix Design by the Euclid Chemical Company37
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As shown, there is no single accepted mix design for pervious concrete. Since
less water is used than typical for conventional concrete, pervious concrete appears
drier and more sensitive to the actual water content. Water reducer and water retarder
are used in most cases. In addition, the amount of water and other materials are varied
with the mixing condition and may need to be adjusted during mixing process. Hence,
the mixing of pervious concrete should be done by a crew who has been trained in a
certification program.
2.7.2 Pervious Concrete Pavement Hydraulic Design
The purpose of hydraulic design is to provide a pavement system in which
water can easily pass through the top layer, be temporarily stored in the subgrade
layer and freely enter a shallow groundwater.
North Carolina Department of Environment and Natural Resources
(NCDENR)38
introduced process of hydraulic design for permeable pavement as
illustrated below:
(1) Select Design Storm
(2) Determine Water Storage Capacity of Pavement
(3) Select Exfiltration Time
(4) Calculate Drawdown (Exfiltration) Time
(5) Compare Actual Drawndown with Design Exfiltration
Following this process, designer can calculate the desirable pavement open
space, which can produce the required drainage at a certain rainfall rate. The
pavement is then designed to have this open space.
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In addition, Malcolm et al.39
developed a program to do the hydraulic design
based on the pervious concrete hydrological analysis program. Input parameters of
the program contains trial thickness of pervious concrete and gravel base, porosity of
pervious concrete and gravel base, local rainfall information, and adjacent areas
which will drain onto pervious concrete. After analyzing the input parameters, the
software can generate a chart to model the flowing situation of rainfall with elapsed
time. Hence, a satisfactory thickness of the pavement and subgrade layers can be
determined by examining the flowing situation.
2.7.3 Pervious Concrete Pavement Structural Design
NCDENR also developed a structural design worksheet for permeable
pavements40
. According to the worksheet, the structural design of pervious concrete
includes four elements: total traffic, in-situ soil strength, environmental elements, and
actual layer design. The primary purpose of the structural design is to examine and
finalize the thickness of subgrade layer. The top layer of pavement is set to the
pervious concrete block, which is usually 6 inches or more. The thickness of pervious
concrete pavement is greater than those of regular concrete that is 4 inches in
normal11
because pervious concrete has lower compressive strength than regular
concrete.
Before beginning the structural design, the thickness of each layer has been
determined from the hydraulic design. Only the thickness of subgrade layer will be
checked in the structural design to determine whether or not the pavement is strong
enough. A formula is given to determine a calculated Structural Number (SNcalc),
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