The effect of mode of loading on the comparison between asphalt rubber and traditional hot mixes laboratory performance

Experience has demonstrated that Asphalt Rubber Hot Mix (ARHM) is particularly effective in inhibiting reflective cracking through thin overlays placed above cracked pavement surfaces. However little numerical work has been published in this area. Numerical computer analysis using finite element approach investigated the predominant mode of loading in reflective cracking and flexural fatigue phenomena in AC pavements and the results suggest that the reflective cracking phenomena is best simulated in the laboratory by executing tests under controlled load by applying a combination of shear and tensile/compressive loads. This paper presents the comparison between the laboratory flexural and reflective fatigue performance of two hot mixes: a traditional mix and a mix modified with Crumb Rubber. Laboratory tests were executed under stress control and strain control both for flexural fatigue tests and reflective cracking tests. Flexural fatigue tests were performed using SHRP–M009 flexural 4-point bending procedure while and reflective cracking tests were performed using the Reflective Cracking Device. The results indicate that mode of loading effects not only affect the number of cycles to failure but the ratios between the failure modes are different for the two types of mixes studied