The Role of Aggregate in Concrete: Exploring the Relationship

Concrete is a mixture of cementitious material, aggregates and water. Generally, aggregates are thought to be an inert filler within a concrete mix. But a closer look reveals the primary role and influence that aggregate plays on the properties of fresh and hardened concrete. Changes in gradation, maximum size, unit weight, and moisture content can alter the character and performance of the concrete mix.

Cement also looks similar to aggregate because it contains sand, one of the most commonly used aggregates. Cement is slightly thicker than aggregate because it is finely ground rock, usually limestone or shale. Strength performance remains the most important property of structural concrete, from an engineering point of view. The relationship between concrete composition and mechanical properties has long been a topic of research interest. Due to the low density of the aggregates used, lightweight aggregate concrete (LWAC) is susceptible to segregation due to differences in the densities of its components.

The concrete samples were produced using two different types of aggregates obtained from crushers with different technical characteristics and river aggregates. Due to moderate hardware and software requirements, methods based on digital imaging methods attracted many researchers to perform efficient and rapid analysis of aggregate characteristics, such as shape index, size distribution, surface texture, etc. Many studies have addressed the recycling of rubber tires as a replacement material for fine or coarse-grained aggregates used in concrete mixes. In addition to strength and durability properties, the textural properties of the aggregate can also affect the properties of hardened concrete. For example, smooth round aggregates make the final product smooth, while angular crushed rocks produce jagged edges and surface texture. The use of aggregates for construction purposes is much more sustainable than the use of cement or concrete.

Cement is more expensive than aggregate because of all the energy used to produce it by heating rocks to extremely high temperatures, so it emits greenhouse gases during this process. It can be manufactured with less expensive aggregate materials, but it is usually the same price as aggregates, if not more expensive. Mohammed and Mahmood used the aggregates they produced from brick fractures as coarse-grained aggregates in the concrete composition and investigated the relationship between coarse-grained aggregate and ultrasonic transition rate using image analysis. Navarrete and Lopez have investigated the relationship between the density and size of coarse-grained aggregates and the degree of concrete segregation. This paste dries and hardens after combining it with water, binding the aggregate once it has been poured into place. If the aggregates are too humid, excess moisture should be subtracted from the expected amount of mixing water.

Not only can aggregate limit the strength of concrete, since aggregate with undesirable properties cannot produce strong concrete, but the properties of the aggregate greatly affect the durability and structural performance of concrete.

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