Asphalt Under-the-Surface

An asphalt road or driveway is multi-layered and engineered for durability and flexibility, consisting of the following layers:

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  compacted subgrade - this is the soil foundation which is compacted and grade for proper drainage and water flow

• sub-base/base course - generally we prefer asphalt but some use aggregate composed of crushed stone or gravel for structural strength and a frost barrier

• binder or intermediate course - a mix of larger aggregates and bitumen that give the road or driveway added strength and binds the surface to the base

• surface course or wearing course - the top layer which is constructed of finer aggregates designed to be smooth, skid-resistant, and waterproo

• tack coat - a sticky substance (emulsion) that we apply between binder and surface layers to increase adhesion