What does the number in the mix type designation represent?

The number in the mix type designation represents the aggregate size in millimeters. This designation is critical as it helps define the physical properties of the asphalt or concrete mix, influencing its performance in various roadway and structural applications. For example, a mix type designated with a specific number indicates the nominal maximum aggregate size used in that mix. This characteristic affects the workability, strength, and durability of the material, making it essential for engineers and planners to use the correct mix designation based on project requirements and expected traffic loads.

In roadway construction, understanding the aggregate size is vital for ensuring the proper balance between durability and flexibility, which are crucial for handling different environmental conditions and traffic stresses. The other options do not accurately reflect what the number represents; traffic class relates to the expected vehicle loads and types, mix durability addresses the longevity and weather resistance of the materials, and structural integrity classification pertains to the overall strength and stability of a structure, none of which are directly indicated by the numerical designation of the mix type.