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Methodology of HMA

construction

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To Be Covered

Hauling

Placement

Compaction

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Tandem Axle End Dump Truck

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Loading of Hot Mix Asphalt in Truck

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Cover the HMA

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Reason For Compaction

To prevent further compaction

To provide shear strength or resistanceto rutting

To ensure the mixture is waterproof

To prevent excessive oxidation of the

asphalt binder

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Temperatureduring construction

Stage of Work Viscosity of Binder Indicated Temperature

Binder at Mixing Max 2 Poise 165-185

Aggregate Temperature 165-185

Mix Temp. at Plant Max 4 Poise 150-170

Mix Temp. at Laying site

Max 5 Poise

130-160

Rolling Temperature Min 115

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Rolling Procedures

Rolling should start as soon as possible afterthe hot mix has been spread.

Rolling consists of three consecutive phases.

1) Breakdown or initial rolling2) Intermediate rolling

3) Finish rolling

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Breakdown rolling compacts the material

beyond the compaction imparted by the

paver, to obtain practically all of the needed

density.

Intermediate rolling densifies and seals the

surface.

Finish rolling removes roller marks and other

blemishes left from pervious rolling

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If rolling causes material displacement, the

affected area are loosened at once with lutes

or rakes and restored to their original grade

with loose material before being re-rolled.

Heavy equipment, including roller should not

be permitted to stand on the finished surface

it has thoroughly cooled

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Rolling freshly placed asphalt

mix is done in the following

order:1. Transverse joints

2. Longitudinal joints3. Initial or breakdown rolling

4. Second or intermediate rolling

5. Finish rolling

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Transverse JointsFirst pass in made with a steel-wheeled roller moving along the

longitudinal joint for a short distance.

This operation should be repeated with successive passes covering 150

to 200 mm (6 to 8 in) of fresh material until the entire width of a drive rollsin on the new mix.

If boards are not used, transverse rolling must 150 to 200 mm short of the

outside edge in order to prevent damage to the edge.

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Longitudinal Joints

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The roller should be shifted to the

previously so that not more then 150 mmrides on the as of newly spread material

This position being shifted graduallyacross the joint until thoroughly

compacted.

Vibration should not be used when

operating on a cold mat.

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Overlapping of Roller Passes

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Rolling Pattern

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For thick lift construction, the rolling process

should start 300 to 375 mm from lower

unsupported edge until certain portion of the

spread is compacted to some stability.

The steel wheeled rollers the operation should

always progress with drive wheel forward in the

direction of paving.

A main reason why breakdown rolling should be

done with the drive wheel is that there ia a some

mor5e direct vertical load applied by this wheel

then tiller wheel.

If the breakdown pass of the roller is made withtiller wheel forward, the pushing force and the

weight is slightly ahead of the vertical, causing

material to push up in front of the wheel.

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Wrong Direction of Roller Wheels

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Advantages of Pneumatic Tires

Roller

1) They provide more uniform degree of

compaction then Tandem Roller

2) They improve the seal near surface

and decreasing the permeability of layer.

3) They orient the aggregate for greatest

stability.

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Finish Rolling

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Paving Operation

The feed truck reverse up to the paver andstops few centimetres in fronts of it. As

the paver approaches, its push rollers

touch the rear wheels of truck.

The hear of mix in front of screed should

uniformly spread over the full pave width.

Distance between surface of mat and

lower edge of Auger flights shouldequivalent to roughly 5 times of max size

of aggregate

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Auger and Limiting Plates for

Auger tunnel

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Head of Mix in front of Screed

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Layer thickness and Grain

size of Mix

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Extracting A Core

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