Aggregate is a vital element in pavement construction. The load
transfer capacity of pavements is significantly impacted by the aggregated. So,
it is recommended to examine the aggregates comprehensively prior to utilize
them in the construction site.
The aggregates should contain the properties like durable and
long-lasting with perfect shape and size so that the pavement can function
monolithically. Aggregates are evaluated for strength, toughness, solidity,
shape, and water absorption.
In order to decide the suitability of the
aggregate for use in pavement construction, The following tests are conducted
to check whether the aggregates are suitable to be utilized in pavement
construction:
In order to decide the suitability of the aggregate for use in pavement
construction, The following tests are conducted to check whether the aggregates
are suitable to be utilized in pavement construction:
1.CRUSHING
TEST: Crushing under compressive stress is a model to check the eligibility of
pavement material for getting passed or failed. A test is organized with IS:
2386 part-IV and applied to find out the crushing strength of aggregates. The
aggregate crushing value offers a relevant measure of resistance to crushing
under increasingly employed crushing load.
2.ABRASION TEST: Abrasion test is accomplished to
examine the rigidity of aggregates as well as determine whether they can be
used for various pavement construction works. Los Angeles abrasion test is
mostly suitable for executing the hardness property and it is implemented in
India (IS: 2386 part-IV).
3.IMPACT TEST: The aggregate impact test is
accomplished to verify the resistance to impact of aggregates. Aggregates which
have passed 12.5 mm sieve and conserved on 10 mm sieve is filled with a
cylindrical steel cup having internal dia 10.2 mm and depth 5 cm that is
connected to a metal base of impact testing machine. The material is covered
with 3 layers where each layer is tamped for 25 numbers of blows. Metal hammer
having weight 13.5 to 14 Kg is set to drop with a free fall of 38.0 cm through
vertical guides and the test specimen is dependent on 15 numbers of blows.
4.SOUNDNESS TEST: Soundness test is conducted to
analyze the resistance of aggregates against weathering action, by carrying out
accelerated weathering test cycles. The Porous aggregates is dependent on
freezing and thawing is liable to decompose beforehand. To determine the
stability of such aggregates, they are dependent on a faster soundness test as
stated in IS: 2386 part-V.
5.SHAPE TESTS: The particle shape of the
aggregate mass is set with the proportion of rough and enlarged particles in
it. Large and enlarged aggregates may be damaged to higher workability and
stability of mixes.
6.SPECIFIC GRAVITY AND WATER ABSORPTION: The
design of concrete and bituminous mixes is mostly based on the properties like
specific gravity and water absorption of aggregates. The specific gravity of a
solid refers to the proportion of its mass to that of an equivalent volume of
distilled water at an indicated temperature. As the aggregates may include
water-permeable voids, so the following two measures of specific gravity of
aggregates are utilized:
1. Apparent specific gravity and
2. Bulk specific gravity.
7.BITUMEN ADHESION TEST: Bitumen is compatible
with all general types of road aggregates on condition that they are dry and do
not contain dust. Without water, no adhesion issue of bituminous construction
occurs.
If the aggregate is wet and cold, the adhesion
issue may happen. This issue can be handled by eliminating moisture from the
aggregate by drying and raising the mixing temperature. Besides, the existence
of water leads to removal of binder from the coated aggregates. This problem
happens if bitumen mixture is absorbent to water.
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PUBLISHED BY
RAJIB DEY
WWW.CONSTRUCTIONCOST.CO
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