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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.


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MATERIAL USED IN HIGHWAY CONSTRUCTION

I. Aggregate

ii. Bitumen and asphalt

iii. Tar

iv. Cement

v. Steel reinforcement.


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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


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Has been widely used since 19201930.

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 repeatedloading 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 comparedwith other paving methods, and perceived ease of repair.

Disadvantages:less durability than other paving

methods,less tensile strength than concrete, the tendencyto become slick and soft in hot weatherand a certain amount of

hydrocarbon pollutionto soil and groundwater or waterways.

BITUMEN AND ASPHALT


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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


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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


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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


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Types And Grades Of Aggregate

Three main types of rock are used to produce

crushed rock aggregates:

IgneousSolidified molten rocks (eg basalt, granite)

SedimentaryCreated by settlement of particles (eg gritstones) or

organic remains (eg limestone) in ancient seas

MetamorphicCreated by heat or pressure (eg hornfels,

quartzites)


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TYPES OF TESTS ON MATERIALS

a.Aggregate Impact Value Testb. Polished Stone Value Test

c. Aggregate Crushing Value Test

d. Flakiness Index Test

e. Elongation Test

f. Penetration Test

g. Softening Testh. Viscosity Test

i. Flash and Fire Point Test

j. Ductility Test

k.Floatation Test

l. Soundness Test.


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Aggregate Impact Value Test

BS 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


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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 sample

iii. Skid resistance measurement.


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Aggregate Crushing Value Test

BS812 : 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


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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


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Flakiness Index Test

BS 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


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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.


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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.


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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.


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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.


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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


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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 beengenerally 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 thelimits of project specifications) a cost-effective

blend and gradation of aggregates and binder that

yields a mix


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Characteristics of asphaltic concrete mix

1.Sufficient binder to ensure a durable pavement;

2. Sufficient mix stability to satisfy the demands oftraffic 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 contentto limit the permeability ofharmful 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.


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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.


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MARSHALL MIX DESIGN METHOD

- Developed by Bruce Marshall & the U.S.

Corps of

Engineers.Objective: To determine the optimum

asphalt content for

a particular aggregate blend and asphalt to

be used.


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PROCEDURES:

1. Prepare asphalt concrete specimens (4 inches in

diameter & 2.5 inches in height) for a range of asphalt

content at and near the estimated optimum asphaltcontent.

(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 content

Typically, 5 different asphalt contents are used.


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ADDING ASPHALT TO AGGREGATE


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MIXING OF AGGREGATE AND ASPHALT


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Placing asphalt

mixture in a

compaction

mold


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Breaking Head

Proving Ring

Flowmeter


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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. % Asphalt

5. Obtain % Asphalt at 4% air voids


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% AC at 4% air voids: 6.7

6. Verify mix design criteria at the optimum

asphalt content. The five mix criteria to

check

against are:(A) Marshall stability

(B) Marshall flow

(C) Air Voids

(D) VMA

(E) VFA


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