Why is specific gravity an important factor in the assessment of coarse aggregate?

• A. It affects the volume of voids in concrete
• B. It determines the color of the aggregate
• C. It influences the thermal conductivity
• D. It indicates the moisture absorption rate

Answer: (A)

Specific gravity is a crucial factor in evaluating coarse aggregate because it directly affects the volume of voids in concrete. When specific gravity is determined, it helps in understanding the density and packing characteristics of the aggregate. A higher specific gravity typically implies that the aggregate is denser, which can lead to a reduction in the volume of voids when the aggregate is compacted in a mix. This is significant because the volume of voids influences the overall strength, durability, and stability of the concrete. Proper control over the volume of voids can affect the water-cement ratio and consequently impact the workability and performance of the concrete.

Other options, while relevant in their own contexts, do not directly tie into the primary reasons why specific gravity is key to assessing coarse aggregate. Color and thermal conductivity may be characteristics of aggregates, but they are not directly influenced by specific gravity in a manner that impacts concrete performance. Similarly, moisture absorption is a separate property; while there may be some correlation with specific gravity, it is not the primary reason why specific gravity is important in assessing coarse aggregate.