A NEW APPROACH TO ASPHALT OVERLAY DESIGN

In the Country Roads Board, which is now the Road Construction Authority of Victoria, the design of asphalt overlays for flexible pavements has for many years been based on the maximum deflection measured under a standard test load. Some limitations have been evident in procedures which have relied solely on this principle, particularly with regard to the control of asphalt fatigue cracking. This paper describes theoretical and field studies which have resulted in modifications to the former approach. Although maximum deflections can be related to vertical compressive strains in the pavement structure they are not always indicative of the potential for fatigue cracking. A simple measure of the pavement curvature under applied load is used to estimate the level of tensile strain in asphalt layers, and thereby to predict fatigue performance. These modifications have been adopted by the Road Construction Authority of Victoria for the analysis of flexible pavements and the design of asphalt overlays. Details of the new procedures are given in the paper as well as examples for their use in predicting the performance of pavements in terms of permanent deformation and surface cracking for different temperature environments. The number of the covering abstract for the conference is TRIS No. 393385. (Author/TRRL)