Why is angularity in coarse/fine aggregates important for compaction?

• A. It enhances moisture retention
• B. It provides interlock during compaction
• C. It improves thermal insulation
• D. It reduces the weight of the mixture

Answer: (B)

Angularity in coarse and fine aggregates is crucial for compaction primarily because it provides interlock during the compaction process. When aggregates are angular rather than rounded, the points and edges of the particles can interlock with one another, creating a denser packing arrangement. This interlocking feature allows for better mechanical stability within the aggregate structure, as the particles resist movement when subjected to compactive forces. Therefore, a mix of angular aggregates can achieve higher density and increased strength in constructed pavements and other surfaces, which is critical for their durability and load-bearing capabilities.

The other aspects mentioned, such as moisture retention, thermal insulation, and weight reduction, do not directly relate to the compaction effectiveness that angularity provides. While moisture retention is important for the performance of certain types of aggregates, it is not a primary reason related to angularity's impact on compaction. Similarly, thermal insulation and weight considerations involve different characteristics of materials that do not primarily depend on the angularity of the aggregates. Thus, the interlocking mechanism facilitated by angular particles is the key reason why angularity is significant for effective compaction.