TOPIK 4 PEMBINAAN JALANRAYA TURAPAN LENTUR

TOPIC 4 CONSTRUCTION OF THE FLEXIBLE PAVEMENT

INTRODUCTION

The pavement is the hardest layer of the road structure. It does not include the side walk of
the road. Its location is on the ground formation on sub-grade. It is away of traffic. The nature of
the soil is usually not strong enough to stand the weight of the heavy vehicles and does not have a
balanced surface. That is why the pavement layer should be constructed on original ground
surface so that the force can be divided equally. This is to ensure that road user will have a save
and comfortable journey. There are two types of pavement, namely Flexible Pavement and Rigid
Pavement.

STRUCTURE OF FLEXIBLE PAVEMENT

Flexible pavement is any kind of pavement that is not constructed using concrete. In
Malaysia the pavement is commonly, constructed by using flexible pavement. Pavements with very
low flexural strength and are flexible in their structural behaviour when under a load are called
flexible pavements. The layers of this type of pavement reflect the deformation of the lower layers
that are beneath the top surface. Thus, if the lower layer is deformed, the surface of the pavement
will also be deformed.

The structure of the road mainly consists of the following layers.
i. Sub-grade soil or simply sub-grade.
ii. Sub-base.
iii. Road Base.
iv. Surface layer.

Surface layer Construction
Depth
Road Base

Sub-base
Sub-grade is the natural

soil beneath road
cfoignustrreuc6t.i1on

Figure 4.1

FUNCTIONS OF FLEXIBLE PAVEMENT

SUB-GRADE

Sub-grade is a layer of natural soil or filled soil, ready to receive the pavement
material over it. Traffic load moving on the surface of the road is ultimately transferred to the
sub-grade through intermediate layer of sub-base, base and surface layer. For the success
full construction of the road, it is necessary that the soil sub-grade should never be over
stressed. Stress intensity on the sub-grade should not be of the magnitude that may cause
excessive deformation in the sub-grade. It is this reason that the strength properties of the
soil sub-grade should be evaluated. The pavement design assumes sub-grade strength as
the basis for designing the pavement. If strength properties of the sub-grade are inferior to
the expected ones, it is given suitable treatment to impart improvement in its performance.

There are a number of tests which can be used to measure strength properties of the
soil sub-grade. All these tests are empirical and are useful in their correlation in the design.
Following are some of the standard tests, used to evaluate the strength properties of the
soil.

1. C.B.R test
2. Plate bearing test
3. Triaxial compression test

SUB-BASE

Sub-base is one course that is constructed with quality materials. This is the lowest
layer of pavement that is constructed onto the sub-grade. The functions of sub-grade:

 Support the road base and spreads the force to the sub-grade.
 Prepares the drainage using rough materials.
 Prepares a cover at any layer that is constructed.
 Bears the pressure from heavy vehicles so the sub-grade will not crack.
 Prevent the sub-grade from traffic flow.

BASE

Base or road base is the main course to absorb force from surface directly and
spread the force to the thickest layer. This layer is normally made from broken stones which
may be bounded or unbounded. It is used to help spread traffic load on large area of sub-
grade so that the stress intensity remains within the capabilities of the sub-grade. Thus
undue deformation caused by the consolidation of the sub-grade is prevented. This layer is
evaluated by plate bearing test.

SURFACE

The surface is the top layer in a pavement. The pavement is divided into two layers
that is Base course and wearing course on the top.

a. Base Course
In resurfacing, this layer is usually known as a binder course. It is the second layer
before the wearing course. The function is to spread the force from the surface.

b. Wearing Course
The wearing course is the top most layers in a pavement. The functions of this layer
are as follows:
 Provides smooth and dense ridding surface.
 Takes up wear and tear due to traffic.
 Provides water tight surface against filtration of surface water.
 Provides hard surface which can withstand the pressure exerted by tyres of

vehicles.

FLEXIBLE PAVEMENT CONSTRUCTION PROCESS

PREPARATION SUB-GRADE LAYER

Prepare the sub-grade layer, it is done after placing the drainage system, piping and
electric cable. The sub-grade surface will be compacted levelled and be cut to make camber
as in plan. If the material of the soil did not have a good quality, it will be changed with
suitable material.

Base formation covers with 50-75mm sand layer or quarry dust and will be
compacted with 8-10 tone compactors. This job must be done to prevent the clay from
absorbing into the stone layer of sub-base and reduce the shear strength of the pavement.

CONSTRUCTION AND COMPACTING THE SUB-BASE

After the sub-base has been prepared with list materials, it will be placed and
constructed into two layers if the thickness is more then 150mm. Every layer will be
compacted according to the plan. Sub-base layer must be compacted carefully with
compactor machine. Compactors with rubber roller can compact 120mm layer in 12 times.
Compacting should start from the side of the road hen slowly towards the middle of the road
in horizontal way. In super-elevated bends compaction machine will start at the lowest part
and slowly towards the higher level. The finished part not be more than 20mm from the plan.

CONSTRUCTION OF ROAD BASE

Before road base is constructed, sub-grade surface and sub-base must be formed
perfectly and compacted enough. The lowest layer and sub-base must be prepared at least
distance of 200m from the base construction.

The road base in Malaysia is commonly constructed with a material known as
crusher run. This material is place and compacted to on the surface of the road. The road
base must be constructed in two layers of same thickness. Each layer should not exceed
150mm.

CONSTRUCTION OF ROAD SURFACE

The road surface is constructed with bitumen materials, such as concrete asphalt,
macadam bitumen and so on. The constructed should be free from dust and waterproof. To
construct the surface layer, the base course must be prepared first. Prime coat is poured
onto the road base surface to be a binder between the road bases and the base course. To
pour the prime coat, the temperature must be according to the specifications stipulated.

Base course is built on one layer only with a pavers’ machine. After this layer is
constructed, it is placed before it is compacted. The surface is checked and corrected if
there are any differences.

The compacting must be done immediately. It should be compacted from the side
towards the middle of the road. It there is a super elevated bend, then it should be
compacted from lower part to higher part. The type of compactors must be according to the
specifications.

Finally wearing course is prepared. Like always, base course should be cleaned
before tack coat is poured. The compacting job is done the same way as the base course.

HOPPE BITUMEN HAD
R BEEN PAVEMENT

ELEVATION LEVELLING
WIRE

HOPPER CONVERYER BITUMEN
CONVERYER PAVEMENT

PUT AND FIT

PLAN

Figure 4.0 : Construct Bitumen Highway
Machine