ABSTRACT
In the UK, the term ‘thin surface course system’ is used widely and many assume that it is the name of a type of asphalt mixture. Asphalt concrete (AC)/open bitumen macadams has been used widely for all layers on local roads because of their relatively low cost resulting from the low binder content, the most expensive component in asphalt. Stone Mastic Asphalt is an asphalt mixture that is standardised in EN 13108-5 that is based on aggregate interlock to maximise its deformation resistance and with the remaining voids filled with mortar. It was developed in Germany as a composite between AC and mastic asphalt in order to overcome abrasion by studded tyres, subsequently solved by banning those tyres. The stiffness of Porous Asphalt is generally lower than that of other asphalt types because of its open structure and, as such, is not generally used in other structural layers, particularly in heavily trafficked pavements.
