Aggregate Testing
Aggregate is the most essential construction material and plays an important role in construction. Aggregate is an inert material which contains 70 to 80 % volume of the concrete. Hence, if you want to know about the concrete, it’s essential to know about aggregate which constitutes a major volume of it. Also, the aggregate is the prime material of the pavement construction because the major portion of the pavement also contains aggregate.
Aggregates influence, to a great extent, the load transfer capability of pavements. Therefore, it is necessary that they should be completely tested before using for construction. Not only the aggregates should be strong and durable but should also have proper shape and size to make the element slab/pavement act monolithically. Hence, it’s important to perform the test on aggregate to ensure the quality of aggregates and check the properties of aggregate.
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.
The Important Properties of Aggregates
- Strength:The coarse aggregates to be used in construction should be sufficiently strong to withstand the stresses. because it’s prime construction material in the building as well as pavement construction.
- Hardness:When the aggregates used in the surface course, its subjected to constant rubbing or abrasion due to moving traffic on the pavement. So, they should be hard enough to resist the wear and tear due to the abrasive action of traffic load. Not much but some amount of abrasion may be induced due to the friction of particle of aggregate in concrete or pavements.
- Toughness: Aggregates used in the construction of buildings and pavements are also subjected to impact due to sudden load in buildings and moving wheel loads on pavements. Hence the resistance to impact is the desirable property of aggregates.
- Durability: The aggregate used in the construction of buildings and pavements should be durable i.e. it should have long life and should resist disintegration due to the weather action. The property of aggregate to withstand the adverse action of weather may be called soundness. Hence aggregate should be sound enough to withstand the weathering action.
- Shape of Aggregates: Shape of aggregate is also the essential property of aggregate because it also plays a significant role in the strength, grading of aggregate and interlocking with each other, which is ultimately responsible for strength.
- Adhesion with Bitumen: : The aggregates used in bituminous pavements should have less affection with water as compared with bituminous material; otherwise the bituminous coating of the aggregates will be stripped off in presence of water.
- Alkali-Aggregate Reaction: Generally, aggregates are the chemically inert material but if the active silica is present in the aggregate, it will be reacting with the alkalis present in the cement, causing expansion and cracking over a period of many years.
- Specific Gravity: Specific gravity is the ratio of the weight of a given volume of aggregate to the weight of an equal volume of water. It’s a quality measure and determine the strength.
- Crushing Test on Aggregate
- Abrasion Test on Aggregate
- Impact Test on Aggregate
- Soundness Test on Aggregate
- Shape Test on Aggregate
- Specific Gravity and Water Absorption Test on Aggregate
- Bitumen Adhesion Test on 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.