What primary function does GSB serve in asphalt mix design?

The primary function of GSB, or Granular Sub Base, in asphalt mix design is crucial for establishing the target spread rate and ensuring that the Voids in Mineral Aggregate (VMA) are within appropriate limits. VMA is a key component in asphalt design as it impacts the durability, stability, and overall performance of the asphalt pavement.

In the context of asphalt mix design, determining the target spread rate helps in optimizing the amount of asphalt and aggregate mix required to achieve the desired compaction and performance characteristics of the pavement. By controlling the VMA, designers can ensure that there is enough void space in the aggregate mix to accommodate asphalt binder, which contributes to the effective adhesion and longevity of the asphalt layer.

Other functions listed, such as calculating mix temperature, identifying aggregate size, and calculating environmental impact, are important aspects of asphalt design but do not specifically relate to the primary role of GSB within the asphalt mix design process. These elements feed into the overall design and implementation of asphalt products, but the focus of GSB on spread rate and VMA directly influences the fundamental properties that determine the quality and performance of the asphalt mix.