Comparison of laboratory test performance between asphalt-rubber hot mix and dense graded asphalt concrete

Abstract

Asphalt-Rubber Hot-Mix (ARHM) has shown a higher resistance to flexural and reflective fatigue cracking, and also to permanent deformation, than conventional Dense Graded Asphalt Concrete (DGAC). Experience has demonstrated that with ARHM, a significant reduction in overlay thickness is possible, especially in cases where the existing pavement is cracked. This paper reports the efforts done on behalf of the Rubber Pavement Association (RPA) to develop a mechanistic design method to quantify the rehabilitation performance of ARHM and DGAC mixes. Based on the results of widely available performance related tests, such as flexural fatigue, repetitive simple shear, wheel track, and permanent deformation tests, combined with traditionally adopted mechanistic-empirical modeling tools, equivalency factors in terms of required overlay thickness have been derived. The results show that to reach the observed overlay thickness equivalency factor of 0.5, a more appropriate modeling tool based on the test results of an appropriate laboratory test done on properly aged specimens is needed. It appears that new modeling tools and test procedures will need to directly consider the phenomenon of reflective cracking.