Pavement Types

1. AGGREGATE ABRASION VALUE
AIM:
To determine the abrasion value of coarse aggregates as per
IS: 2386 (Part IV) - 1963.
i) Los Angles abrasion testing machine
ii) IS Sieve of size - 1.7mm
iii) Abrasive charge - 12 nos. cast iron or steel spheres
approximately 48mm dia. and each weighing between 390
and 445g ensuring that the total weight of charge is 5000 +
25g
iv) Oven

3. PREPARATION OF SAMPLE:
The test sample should consist of clean aggregates which has
been dried in an oven at 105 to 110oC to a substantially constant
weight and should conform to one of the gradings shown in the
table below:

5. PROCEDURE:
The test sample and the abrasive charge should be placed in the
Los Angles abrasion testing machine and the machine rotated at
a speed of 20 to 33 revolutions/minute for 500 0r 1000
revolutions. At the completion of the test, the material should be
discharged and sieved through 1.70mm IS Sieve.
For Grade A - 12 Spheres
For grade B -11 Spheres
For Grade C -8 Spheres
For Grade D - 6 Spheres
For Grade E,F,G - 12 Spheres

6. Reporting Of Results:
1) The material Coarser than 1.70mm is sieved and weighted.
Let it be B.
2) The proportion of loss between A and B should be expressed
as percentage of original weight of sample.
3) The value should be reported as,
Agg.Abrasion Value = (A-B)/B X 100
Where,(A-B) = Weight of aggregate passing Through 1.70mm
B = Weight of Aggregate Taken.

7. AGGREGATE IMPACT VALUE
Aim:
To determine the aggregate impact value of coarse
aggregates as per IS: 2386 (Part IV) - 1963.
Apparatus Required:
i) Impact testing machine conforming to IS: 2386 (Part IV)
ii) IS Sieves of sizes - 12.5mm, 10mm and 2.36mm
iii) A cylindrical metal measure of 75mm dia. and 50mm depth
iv) A tamping rod of 10mm circular cross section and 230mm
length, rounded at one end
v) Oven

10. PREPARATION OF SAMPLE:
i) The test sample should conform to the following grading:-
Passing through 12.5mm IS Sieve and Retention on 10mm IS
Sieve is taken.
ii) The sample should be oven-dried for 4hrs. at a temperature
of 100 to 110oC and cooled.
iii) The measure should be about one-third full with the prepared
aggregates and tamped with 25 strokes of the tamping rod.
A further similar quantity of aggregates should be added and
a further tamping of 25 strokes given. The measure should
finally be filled to overflow, tamped 25 times and the surplus
aggregates struck off, using a tamping rod as a straight
edge. The net weight of the aggregates in the measure
should be determined to the nearest gram (Weight 'A').

11. PROCEDURE:
i) The cup of the impact testing machine should be fixed firmly
in position on the base of the machine and the whole of the
test sample placed in it and compacted by 25 strokes of the
tamping rod.
ii) The hammer should be raised to 380mm above the upper
surface of the aggregates in the cup and allowed to fall
freely onto the aggregates. The test sample should be
subjected to a total of 15 such blows, each being delivered
at an interval of not less than one second.

12. REPORTING OF RESULTS:
i) The sample should be removed and sieved through a
2.36mm IS Sieve. The fraction passing through should be
weighed (Weight 'B').
ii) The ratio of the weight of the fines formed to the total
sample weight should be expressed as a percentage B
Aggregate impact value = B/A x 100%
Where B - Weight Of Passing Through 2.36mm
A – Weight of Aggregate Taken.
iii) Two such tests should be carried out and the mean of the
results should be reported.

13. Types of Pavements
Definition:
Pavement is the actual travel surface especially made
durable and serviceable to withstand the traffic load
commuting upon it.
Pavement grants friction for the vehicles thus providing
comfort to the driver and transfers the traffic load
from the upper surface to the natural soil.
In earlier times before the vehicular traffic became most
regular, cobblestone paths were much familiar for
animal carts and on foot traffic load.
Pavements are primarily to be used by vehicles and
pedestrians.

14. Storm water drainage and environmental
conditions are a major concern in the designing of a
pavement.
The first of the constructed roads date back to 4000 BC
and consisted of stone paved streets or timber roads.
The roads of the earlier times depended solely on stone,
gravel and sand for construction and water was used as
a binding agent to level and give a finished look to the
surface.
All hard road pavements usually fall into two broad
categories namely
– Flexible Pavement
– Rigid Pavement

15. Flexible pavement: Definition
Are those pavements which reflect the deformation
of sub grade and the subsequent layers to the
surface.
Flexible, usually asphalt, is laid with no
reinforcement or with a specialized fabric
reinforcement that permits limited flow or
repositioning of the roadbed under ground changes.
The design of flexible pavement is based on load
distributing characteristic of the component layers.
The black top pavement including water & gravel
bound macadam fall in this category.
Flexible pavement on the whole has low or
negligible flexible strength flexible in their
structural action).

16. The flexible pavement layers transmit the vertical or
compressive stresses to the lower layers by grain
transfer through contact points of granular structure.
The vertical compressive stress is maximum on the
pavement surface directly under the wheel load and is
equal to contact pressure under the wheels. Due to the
ability to distribute the stress to large area in the shape of
truncated cone the stresses get decreased in the lower
layer.
As such the flexible pavement may be constructed in a
number of layers and the top layer has to be strongest
as the highest compressive stresses.

17. To be sustained by this layer, in addition to wear and
tear, the lower layer have to take up only lesser
magnitude of stress as there is no direct wearing
action die to traffic loads, therefore inferior
material with lower cast can be used in the lower
layers.

18. Rigid pavement: Definition
The rigid characteristic of the pavement are associated
with rigidity or flexural strength or slab action so the
load is distributed over a wide area of subgrade soil.
Rigid pavement is laid in slabs with steel
reinforcement.
The rigid pavements are made of cement concrete either
plan, reinforced or prestressed concrete.
Critical condition of stress in the rigid pavement is the
maximum flexural stress occurring in the slab due to
wheel load and the temperature changes.
Rigid pavement is designed and analyzed by using the
elastic theory.

19. Advantages of Rigid Pavement
Rigid lasts much, much longer i.e
30+ years compared to 5-10 years of flexible
pavements.
In the long run it is about half the cost to install and
maintain. But the initial costs are somewhat high.
Rigid pavement has the ability to bridge small
imperfections in the subgrade.
Less Maintenance cost and Continuous Traffic and
Flow.
High efficiency in terms of functionality.

23. Flexible Pavements:
Deformation in the sub grade is transferred to the
upper layers.
Design is based on load distributing characteristics of
the component layers
Have low flexural strength
Load is transferred by grain to grain contact
Have low completion cost but repairing cost is high
Have low life span (High Maintenance Cost)
No thermal stresses are induced as the pavement have
the ability to contract and expand freely

24. That why expansion joints are not needed
Strength of the road is highly dependent on the
strength of the sub grade
Rolling of the surfacing is needed
Road can be used for traffic within 24 hours
Force of friction is less.
Damaged by Oils and Certain Chemicals

25. RIGID PAVEMENTS:
Deformation in the subgrade is not transferred to
subsequent layers
Design is based on flexural strength or slab action
Have high flexural strength
No such phenomenon of grain to grain load transfer
exists
Have low repairing cost but completion cost is high
Life span is more as compare to flexible (Low
Maintenance Cost)
Thermal stresses are more vulnerable to be induced as
the ability to contract and expand is very less in concrete

26. Thats why expansion joints are needed
Strength of the road is less dependent on the
strength of the sub grade
Rolling of the surfacing in not needed
Road cannot be used until 14 days of curing
Force of friction is high
No Damage by Oils and Greases