What is the required minimum compaction for wearing and binder course based on material sampled from the road site?

The requirement for minimum compaction of wearing and binder courses is set to ensure that the asphalt mix achieves optimal density, stability, and durability, which are crucial for performance under traffic loads and environmental conditions. Attaining 96% of the Marshall density reflects a balance between compaction and workability, allowing sufficient bonding while avoiding potential issues such as rutting or cracking.

The choice of 96% is significant because it is high enough to achieve the necessary mechanical properties of the asphalt, contributing to the structural integrity of the pavement layer, while also allowing some level of flexibility that is essential for accommodating thermal expansion and contraction. This level of compaction provides a practical approach for asphalt layers to withstand the effects of traffic and weather over time.

In contrast, higher levels of compaction, such as 98% or 100%, may be overly rigid and could lead to challenges in terms of workability and placement. Conversely, a lower compaction level like 94% may not provide adequate strength and stability, potentially leading to early pavement failure. Thus, 96% of the Marshall density strikes an effective balance, ensuring durability while facilitating proper installation processes.