SUB BASE MATERIALS
Sub base materials make up the load bearing layer directly beneath the overlying surface bed, it serves as the foundation for the overall top structure. Layers are formed by spreading the aggregate in thin layers and the compacting it with heavy equipment until the aggregate forms a dense layer of interlocking aggregate. The aggregate is composed of sand, gravel, crushed rock, crushed recycled building rubble and other natural mineral materials that provide the necessary strength and durability. The aggregate must meet specific gradation requirements.