Accelerated Pavement Testing to Compare Efficiency of Overlay Materials Used in Brazil

In Brazil, asphalt rubber (AR) has been used to delay reflection cracking in overlays since the 1990s. To quantity reflection cracking evolution in AR and asphalt concrete (AC) overlays, an accelerated pavement testing (APT) study was carried out by the Federal University of Rio Grande do Sul and the State Roads Department. Overlays 5.0-cm thick were set on sections with identical structures (severely cracked AC wearing course and granular base), and from March 2003 to February 2005 a traffic simulator applied 100-kN axle loads on the two full-scale pavements. During the tests, cracks were recorded, and deflections and strains were measured. APT raw data suggested that the efficiency of the AR overlay in delaying reflection cracking was 5.55 times greater than that of the AC overlay. Because the overlays were tested in different seasons, a supplementary laboratory study was carried out to quantify temperature effect on AC and AR resilient modulus, later used in a fatigue analysis. With APT and fatigue analysis data combined, it was possible to ascertain that if both overlays were tested at identical pavement temperatures, the efficiency of the AR overlay delaying reflection cracking would be 4.84 times greater than that of the AC overlay.