Practical verification of the theory behind long-life asphalt pavements

Abstract

Traditional asphalt pavement design is based on a mechanistic-empirical approach which identifies the strain at critical locations in the pavement structure to safeguard the road against fatigue and structural deformation. However, research has shown that when roads are well built above a certain threshold, structural damage is non-existent with rutting confined to the surfacing, an ideal and economic design solution. The existence of these 'long-life' pavements challenges the current design and maintenance methodologies and suggests a need for a radical approach to pavement design. Although findings from global research have verified that a threshold effect for pavements does exist, there is limited real life data to support this theory. This paper, sponsored by Highways England, aims to demonstrate the threshold effect as well as develop a radical approach to flexible pavement design and maintenance, using the threshold concept. Three instrumented road sections of varying thicknesses were designed, built, and trafficked under varying wheel loads and speed. The results demonstrated classical pavement deterioration through both rutting and fatigue cracking. However, one of the sections showed no deterioration and the associated strains illustrate the threshold effect. In addition, a methodology is presented which involves the development of a robust model that predicts tensile asphalt strains directly from falling weight deflectometer (FWD) measurements which could be used as a tool to identify long life pavements on the English Strategic Road Network (SRN).

Fatigue Life Prediction of Long-Life Pavement Using Frequency-Domain Analysis

“…Pavement fatigue means that the internal performance of the material becomes worse under repeated loads (generally smaller than static loads). Fatigue life is the span from its beginning to the time when fractures occur under load, or the cycle times of the stress or strain experienced before fatigue failure [5][6][7][8].…”