What is a key characteristic that contributes to durability in mix design?

A key characteristic that greatly contributes to durability in mix design is resistance to environmental degradation. This aspect emphasizes the ability of the materials used in a mix to withstand various environmental factors such as moisture, temperature fluctuations, chemical exposure, and wear over time. Durable mixes are crucial for maintaining performance under these conditions, ensuring that the structure remains intact and functional throughout its intended lifespan.

Factors like the color of aggregates, availability of materials, and cost-effectiveness, while relevant in specific contexts, do not directly relate to the long-term performance and resilience of the mix. For example, the color of aggregates may play a role in aesthetics but does not affect durability. The availability of materials relates more to logistical considerations rather than the intrinsic properties imparted to the concrete or asphalt. Similarly, cost-effectiveness is important for project budgeting but does not guarantee that the mix will perform well under stressors that could lead to degradation over time. Thus, the focus on environmental resistance makes choice B the most pertinent characteristic influencing the durability of mix design.