Various types of tests conducted to verify the quality of aggregates in road work

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:

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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Various types of tests conducted to verify the quality of aggregates in road work