ASPHALT MIX DESIGN AND CONSTRUCTION: A SELECTION OF POSSIBLE PITFALLS

Every year large volumes of asphalt are paved on roads, streets, airports and other pavements in southern Africa. The requirements in terms of performance of some of these asphalt pavements are high due to severe environmental or loading conditions. Failures in asphalt layers occurs regularly on asphalt projects in southern Africa. Most of these failures in asphalt pavements can be attributed to some problem during the mix design, manufacturing or paving operation. The paper describes lessons learnt from asphalt failures and problems experienced during the last few years on a number of projects in southern Africa. It provides a look at various asphalt mix design and construction factors, as experienced on actual projects, that may result in problems or defects that leads to various distress types, including deformation, stripping, high permeability and premature cracking. Examples from actual projects are presented. The paper concludes with the factors that repeatedly results in problems with asphalt mixes and that should be kept in mind during the design, manufacturing and paving of asphalt mixes