ABSTRACT
A flexible pavement is built up in layers of bound asphalt over a foundation of unbound aggregate, again often in several layers. The thickness of the base layer is dependent on the loading applied and the strength of the asphalt and can be several hundred millimetres in total. Surface courses were traditionally 40 mm thick, but they were increased for hot rolled asphalt to minimise loss of chippings due to premature cooling during construction and were reduced in other materials to minimise the use of material, particularly scarce high polished stone value aggregate. The use of reclaimed asphalt to replace some of the aggregate should not affect the properties of the mixture type if the mixture is properly designed and the quality control is sufficient. Reducing the nominal maximum aggregate size generally improves the resistance to scuffing of a mixture. Therefore, mixtures with smaller nominal maximum aggregate size are often used for roundabouts and other areas of high stress.
