Aggregate plays an important role in construction. Aggregates influence, to a great extent, the load transfer capability of pavements. Therefore, it is necessary that they should be completely tested before slabs using for construction. Not only the aggregates should be strong and durable, aggregates should also have proper shape and size to make the element pavement act monolithically.
The aggregates are tested for strength, toughness, hardness, shape, and water absorption. Different types of test on aggregate like impact test, abrasion test, crushing value test, soundness test, etc. are carried out to decide the suitability of aggregate.
Different Types of Test on Aggregate:
In order to decide the suitability of the aggregate for use in concrete/pavement construction, following tests are carried out:
01. Crushing Test on Aggregate:
The aggregate crushing value gives a relative measure of the resistance of an aggregate crushing under gradually applied compressive load. If the aggregate crushing value is less than 10, it signifies an exceptionally strong aggregate. While crushing value above 35 would normally be considered as weak aggregates.
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02. Abrasion Test on Aggregate:
To determine the abrasion value of the coarse aggregate, this test is carried out. The principle of Los Angeles abrasion test is to find the percentage wear due to relative rubbing action between the aggregate and steel balls used as an abrasive charge.
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03. Impact Test on Aggregate:
The aggregates should have sufficient toughness to resist their disintegration due to the impact. This distinctive property is measured by impact value test.
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04. Soundness Test on Aggregate:
The soundness test is carried out to learn the resistance of aggregates to weathering actions like thawing, freezing, alternate wetting and drying in normal condition and in salt water, variation in temperature.
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05. Shape Test on Aggregate:
Flakiness index test is used to determine the particle shape of the aggregate. It is defined in percentage by weight of aggregate particles and least dimension (thickness) of those particles should not be less than 0.6 times their mean area.
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06. Specific Gravity and Water Absorption Test on Aggregate:
The specific gravity of an aggregate is a measure of a strength or quality of the material. The specific gravity test helps in the identification of stone. Water absorption gives an idea about the strength of the aggregate.
07. Bitumen Adhesion Test on Aggregate:
Bitumen gets attached well to all normal types of road aggregates provided they are dry and free from dust. In the absence of water, there is no adhesion problem of bituminous construction. Adhesion problem may occur when the aggregate is wet and cold. This problem can be dealt with by removing moisture from the aggregate by drying and increasing the mixing temperature.