Porous asphalt as a road surfacing material has been under investigation by TRL since 1967 and is now included in the Specification for Highway Works and the Design Manual for Roads and Bridges published by the Department of Transport and the other Overseeing Departments for UK trunks roads. The experience gained from extensive road trials is reviewed and recommendations are derived to assist those involved in the design, manufacture and application of porous asphalt, particularly with a 20 mm nominal aggregate grading. The road trials are interpreted in terms of the design and construction of porous asphalt layers; the properties that can be achieved from the material; and the maintenance implications of its use. The road trials have shown that porous asphalt can be durable if it is properly designed and constructed and it is laid on suitable sites. For such situations, the standard properties required of surface course materials (such as skid-resistance, texture depth and profile) can be provided by porous asphalt, together with the additional benefits through reduction of noise and spray. Aspects of maintenance for porous asphalt that are different from that of traditional, impervious surfacings are discussed. (A)
Abstract