pavement overlay

PAVEMENT OVERLAY- SITE VISIT

Prepared by- Simranjit Singh /Amit Aneja /Aman Pabbi

ACKNOWLEDGEMENT

The authors would like to express special thanks of gratitude to Prof.

AK Duggal for his immense guidance, and providing a first hand experience of

working on actual site.

We are grateful for his cooperation and his zeal to impart knowledge to the

minds of tomorrow, for a better future.

2 Authors- Simranjit Singh/ Amit Aneja/ Aman

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CONTENTS

Purpose of Visit

Introduction

Need for Overlay

Slurry Seal Coat

Equipment used

Check for thickness of Overlay

Sampling

Problems faced on site

Important Notes


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PURPOSE OF VISIT

The visit aimed at introducing the students to the overlaying process of a

pavement in practical.

To familiarize the students with the problems that frequently occur at

site.

The equipment used for highway maintenance, overlay.

To educate the students to measure the thickness of the overlay.

The procedure for sampling, for quality testing of the mix.


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INTRODUCTION

Overlay is a practice of highway maintenance, by adding a layer to the

existing pavement surface.

Various factors to be considered for the design of the overlay are-

1. Surface conditions of the existing road

2. Structural conditions

3. Relative vertical displacement

4. Surface texture.


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NEED FOR OVERLAY

The strength of the pavement as

was measured using Benkelman

beam method was satisfactory.

Overlay is provided because of the

problem of slippage.

Earlier the pavement on the

opposite carriageway was treated.

Strength for that was also found to

be satisfactory using Benkelman

beam method.

At some location cracks were

observed, and hence it was treated

using a Slurry Seal Patch (Pictures

2 & 3).

Picture-1


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SLURRY SEAL COAT

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Slurry seal coat/patch

For reference, here only a small portion is covered with the slurry seal coat

hence for reference, it is referred to as slurry seal patch.

As shown in picture-2, marked with red circle, are cracks on the pavement.

Such cracks have been repaired using stone dust, fine grit and bitumen.

Bitumen content here is greater than 6%.

Picture-2 Picture-3

Authors- Simranjit Singh/ Amit Aneja/ Aman

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EQUIPMENTS USED

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1. Paver Finisher

Equipment as shown in pictures 4 and

5.

This is used for laying the mix as a

loose course.

Loose laying for the desired 40mm

compacted thickness was 52mm.

Tipper is connected to the rear of the

paver at points marked by a circle in

picture-5.

Picture-4

The paver is moved in reverse

direction with the connected tipper

in neutral gear.

The mix moves through the

conveyor belts forward to the

screed which spills it.

Picture-5

Conveyor

Belts


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EQUIPMENTS USED

9

2. Tar boilery

Equipment is as shown in pictures 6 and

7.

Normally tractor mounted.

With heating arrangement to keep

bitumen in hot/ molten state.

Picture-6

Picture-7

Pressure gauge as shown in

picture-7.

This indicates the pressure at

which bitumen is to be released.


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EQUIPMENTS USED

10

3. Nozzles

As shown in picture-8.

It should be insulated,

such that it is easy to

handle by the labor

(Picture-9)

This is used for tack coat.

4. Tipper

As shown in picture-10.

The rear of the tipper is

mounted to the rear of the

paver, such that the

material supply is

continuous to the conveyor

belts for spread through

the screed.

Picture-9 Picture-8

Nozzle

Picture-10


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EQUIPMENTS USED

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5. Compaction Roller

The rollers used for compaction are

Vibratory Rollers (Picture-11)

Smooth Wheel Roller (Picture-

12)

Initial compaction is done using

Vibratory rollers.

Picture-11

Picture-12

In certain cases, where there are

structures (nearby buildings) on

soft soils, vibratory rollers are

not preferred as they can cause

settlement of those foundations.


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12

Check for thickness

This is done in 2 steps:

1. Driving a nail through the

pavement vertically.

2. Measuring the depth by vernier

callipers.

NOTE- Nail should be driven till the

striking sound of changes, indicating the

pavement layer beneath.

Sampling

Sample for testing the quality of

mix (like checking of bitumen

content in mix) is taken from the

paver itself, i.e. the mix being

actually laid on site.

Picture-13

Picture-14 Nail

Sample

CHECK FOR THICKNESS / SAMPLING


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PROBLEMS FACED ON SITE

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1. Loose material along Pavement Edges

As seen clearly in picture-15 the material along

the edges in loose state, showing poor

compaction along the edges.

2. Camber

It was observed at the site, the thickness of

overlay near the edge was 40mm, and that

reduced to 39mm towards the center.

Proper camber needs to be maintained to avoid

accumulation of water on the pavement as it

could be disastrous.

Picture-15

Pavement

Edge


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IMPORTANT NOTES

Date of visit – 23rd April, 2014.

Location – Road opposite Kalagram, Chandigarh-Panchkula Road.

NITTTR is the 3rd party for quality control in this project, under leadership

of Prof. AK Duggal.

Loose thickness of overlay = 52mm, from paver.

Overlay consists of a 40mm compacted layer of Bituminous Concrete.

The slurry seal patch on the other carriageway has a bitumen content

greater than 6%, designed by NITTTR.


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pavement overlay

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