1

CHAPTER 3 : PAVEMENT MATERIALS

• Road surface or pavement is the durable surface material laid down on an area intended to sustain vehicular or foot traffic, such as a road or walkway.

• In the past cobblestones and granite setts were extensively used, but these surfaces have mostly been replaced by asphalt or concrete.

2

MATERIAL USED IN HIGHWAY CONSTRUCTION

I. Aggregateii. Bitumen and asphaltiii. Tariv. Cementv. Steel reinforcement.

3

• Coarse particulate material used in construction, including sand, gravel, crushed stone, slag, recycled concrete and geosynthetic aggregates.

• Aggregates are a component of composite materials such as concrete and asphalt concrete

• Aggregate serves as reinforcement to add strength to the overall composite material.

• Due to the relatively high hydraulic conductivity value as compared to most soils, aggregates are widely used in drainage applications such as foundation and french drains, septic drain fields, retaining wall drains, and road side edge drains.

• Aggregates are also used as base material under foundations, roads, and railroads.

AGGREGATE

4

• Has been widely used since 1920–1930. • The terms asphalt and bitumen are often used interchangeably to

mean both natural and manufactured forms of the substance. In American English, asphalt (or asphalt cement) is the carefully refined residue from the distillation process of selected crude oils. Outside the U.S., the product is often called bitumen.

• The viscous nature of the bitumen binder allows asphalt concrete to sustain significant plastic deformation, although fatigue from repeated loading over time.

• Most asphalt surfaces are laid on a gravel base.• In areas with very soft or expansive subgrades such as clay or

peat, thick gravel bases or stabilization of the subgrade with portland cement or lime may be required.

• Asphalt is categorized as hot mix asphalt (hma), warm mix asphalt, or cold mix asphalt.

• Hot mix asphalt is applied at temperatures over 300 F• Warm mix asphalt is applied at temperatures of 200 to 250

degrees F• cold mix asphalt is often used on lower volume rural roads, where

hot mix asphalt would cool too much on the long trip from the asphalt plant to the construction site.

• Advantages: low noise, relatively low cost compared with other paving methods, and perceived ease of repair.

• Disadvantages:less durability than other paving methods, less tensile strength than concrete, the tendency to become slick and soft in hot weather and a certain amount of hydrocarbon pollution to soil and groundwater or waterways.

BITUMEN AND ASPHALT

5

• Cement is a binder, a substance that sets and hardens independently, and can bind other materials together.

• The word "cement" traces to the romans

CEMENT

6

• Cement is made by heating limestone (calcium carbonate) with small quantities of other materials (such as clay) to 1450 °C in a kiln.

• The resulting hard substance, called 'clinker', is then ground with a small amount of gypsum into a powder to make 'Ordinary Portland Cement', the most commonly used type of cement (often referred to as OPC).

• Portland cement is a basic ingredient of concrete, mortar and most non-speciality grout.

• The most common use for Portland cement is in the production of concrete.

PORTLAND CEMENT

7

• Also known as reinforcing steel, reinforcement steel, or a deformed bar, is a common steel bar, and is commonly used as a tensioning device in reinforced concrete and reinforced masonry structures holding the concrete in compression.

• usually formed from carbon steel, and is given ridges for better mechanical anchoring into the concrete.

• Rebar is available in different grades and specifications that vary in yield strength, ultimate tensile strength, chemical composition, and percentage of elongation.

• The grade designation is equal to the minimum yield strength of the bar in ksi (1000 psi) for example grade 60 rebar has a minimum yield strength of 60 ksi. Rebar is typically manufactured in grades 40, 60, and 75.

STEEL REINFORCEMENT

8

Types And Grades Of Aggregate

Three main types of rock are used to produce crushed rock aggregates:

Igneous Solidified molten rocks (eg basalt, granite)

Sedimentary Created by settlement of particles (eg gritstones) or organic remains (eg limestone) in ancient seas

Metamorphic Created by heat or pressure (eg hornfels, quartzites)

9

TYPES OF TESTS ON MATERIALS

a.Aggregate Impact Value Testb. Polished Stone Value Testc. Aggregate Crushing Value Testd. Flakiness Index Teste. Elongation Testf. Penetration Testg. Softening Testh. Viscosity Testi. Flash and Fire Point Testj. Ductility Testk.Floatation Testl. Soundness Test.

10

Aggregate Impact Value TestBS 812: Part 112: 1990

• Determine aggregate resistance due to impact.• Size aggregate : passing sieve 14mm and retain 10

mm.• Agregate were filling into mould in one layer and will be

driven by rod in 25 times.• Aggregate mass will be taken.• Hammer with 13.5 to 14 kg will be release from the

height of 380mm and will driven in a 15 times on aggregate.

• After finished, aggregate will be sieve with size of sieve is 2.36 mm.

• AIV were determine with a formulae :

AIV = mass of aggregate passing sieve of 2.36 mm x 100 % total mass

< 30 % - pass>30 % fail

11

Polished STone Value Test

• Only conducted on aggregate that be used as a wearing coarse.• Polishing value of aggregate show of aggregate resistance due to

wheel vehicles.• Polishing level affect skid resistance of pavement.• This test consist 3 stages:

i. Sample preparationii. Polishing sampleiii. Skid resistance measurement.

12

Aggregate Crushing Value TestBS812 : Part 110 : 1990

• To determine the strength of aggregate resistance to crushing under the applied compressive load.

• Normal size : passing 14 mm sieve and 10 mm retain ( 3000 g )• Aggregate were fill into mold in three layers and each layer were

driven by 25 times.• Then inserted into the compression machine for 10 minutes and

will be compress by 400 KN load.• Aggregate will be sieve in in 2.36 mm sieve and the mass will be

determined.

ACV = mass of aggregate passing sieve of 2.36 mm x 100 % total mass

13

Elongation Index BS812 : Part 1: 1975

• To determine the percentage of the longest aggregate.• Classified longest when longest dimension is more than 1.8

times from average size.• Aggregate size to be tested is 63 mm to 6.3 mm.

EI = Retain mass x 100 % Total mass

14

Flakiness Index TestBS 812 : Section 105.1 : 1989

• Purpose : To determine percentage of flat aggregate.• Classified as flat when the thickness is less than 0.6 of average

size.• Aggregate to be tested is in size of 63 mm to 6.3 mm

FI = Mass of aggregate passing x100 % Total mass

15

Penetration Test(AASHTO T49-84)

• To determine the hardness of the material.• Defined as the distance (in 1 / 10) standard needle puncture

of the time, load and temperature are known.• Using a standard needle under the load of 100 grams for 5

seconds at a temperature of 20 degrees celsius.• High penetration value indicates the material is soft.

16

SOFTENING TEST

• To determine the temperature at which phase changes occur in the bitumen.

• Soft spot is defined as the temperature at which bitumen is unable to support the steel ball and began to soften.

17

VISCOSITY TEST

To determine the viscosity of the bitumen.Defined as the resistance of a fluid to flow.Two types of viscosity : absolute or dynamic viscosity and kinematic.

18

Flash and Fire Point Test

When the bitumen is heated at high temperatures, the vapor will be liberated and embrace if any sources of ignition.Flash point indicates the temperature at which bitumen can be heated without danger of fire generated in the presence of the fire.The method used is the Cleveland open cup method.

19

DUCTILITY TEST

This test is done to determine the ductility of distillation residue of cutback bitumen, blown type bitumen and other bituminous products as per IS: 1208 – 1978. The principle is : The ductility of a bituminous material is measured by the distance in cm to which it will elongate before breaking when a standard briquette specimen of the material is pulled apart at a specified speed and a specified temperature.

The apparatus required for this test: i) Standard mould ii) Water bath iii) Testing machine

20

ASPHALT MIX DESIGN

21

Objectives of asphalt mix design The design of an asphalt mix is largely a matter of selecting and proportioning materials to optimise the engineering properties in relation to the desired behaviour in service. Procedures for designing asphalt mixes have been generally developed around testing of dense graded mixes and determination of optimum binder content, although most tests can be used for other mix types with suitable interpretation of results.The overall objective for the design of dense graded asphalt paving mixes is to determine (within the limits of project specifications) a cost-effective blend and gradation of aggregates and binder that yields a mix

22

Characteristics of asphaltic concrete mix

1.Sufficient binder to ensure a durable pavement; 2. Sufficient mix stability to satisfy the demands of traffic without distortion or displacement; 3. Sufficient voids in the total compacted mix to allow for a slight amount of in place compaction by traffic and bitumen expansion due to temperature increases, without flushing, bleeding and loss of stability; 4. A maximum void content to limit the permeability of harmful air and moisture into the mix; 5. Sufficient workability to permit efficient placement of the mix without segregation and without sacrificing stability and performance; 6. For surface mixes, proper aggregate texture and hardness to provide sufficient skid resistance.

23

An overview of the design process Asphalt mix design involves the following basic steps that are similar in concept, regardless of the actual tests and procedures used: 1. Selection of mix type. 2. Selection of component materials. 3. Combination of aggregates to meet target grading. 4. Selection of target binder content or range.5. Mixing and compaction of asphalt mix to a density that is representative of in-service conditions. 6. Measurement of volumetric properties of compacted mix. 7. Mechanical testing of compacted samples, if required. 8. Verification of design properties on samples of manufactured asphalt, if required. 9. Selection of Job Mix.

24

MARSHALL MIX DESIGN METHOD- Developed by Bruce Marshall & the U.S. Corps ofEngineers.Objective: To determine the optimum asphalt content fora particular aggregate blend and asphalt to be used.

25

PROCEDURES:1. Prepare asphalt concrete specimens (4 inches indiameter & 2.5 inches in height) for a range of asphaltcontent at and near the estimated optimum asphalt content.(A) Mixing temperature:at asphalt viscosity of 170 ± 20 cSt(B) Compaction temperature:at asphalt viscosity of 280 ± 30 cSt(C) Compactive Effort:35, 50 or 75 blows with a Marshall hammer(10 lbs, 18 inches drop) on each side of the specimen.(D) Number of Samples:3 replicates at each asphalt contentTypically, 5 different asphalt contents are used.

26

ADDING ASPHALT TO AGGREGATE

27

MIXING OF AGGREGATE AND ASPHALT

28

Placing asphaltmixture in acompactionmold

29

Breaking Head

Proving Ring

Flowmeter

30

4. Plot (A) Marshall Stability v.s. % Asphalt(B) Marshall Flow v.s. % Asphalt(C) % Air Voids v.s. % Asphalt(D) Bulk Density v.s. % Asphalt(E) % VMA v.s. % Asphalt(F) % VFA v.s. % Asphalt5. Obtain % Asphalt at 4% air voids

31

32

% AC at 4% air voids: 6.76. Verify mix design criteria at the optimumasphalt content. The five mix criteria to checkagainst are:(A) Marshall stability(B) Marshall flow(C) Air Voids(D) VMA(E) VFA

33

34

35

36

37

38

39