Detecting Resilient Response of Asphalt Concrete among Various Testing Techniques

Abstract

Determination of resilient modulus of asphalt concrete is recommended by the Superpave system to be obtained from the repeated indirect tensile stress test and be implemented in the pavement design. Loading mode of asphalt concrete specimen is an important issue, although it is under-estimated issue for the detection of asphalt concrete resilient modulus. In The present work, a laboratory investigation conducted to verify the possibility of obtaining the resilient response of asphalt concrete in terms of resilient modulus, permanent deformation, and strength under repeated tensile, shear, flexure, and compressive stresses. Beams and cylindrical specimens of Asphalt concrete have been prepared at optimum asphalt content. Extra specimens having 0.5 % of asphalt binder content above and below the optimum value have also been prepared. Testing of specimens was conducted using the Pneumatic Repeated Load System PRLS at 25° C under repeated compressive, tensile, flexure, and shear stresses. The permanent deformation was monitored through LVDT (Linearly Variable Differential Transformer). The applied stress level was 138 kPa in the form of rectangular wave. A constant loading frequency of 60 cycles per minute was implemented. It includes 0.1 second of load duration and 0.9 second of rest period. The resilient modulus, permanent deformation, and strength properties were determined and compared among the various testing techniques. It was concluded that the resilient modulus (Mr) varies depending on the size of specimen, and mode of testing. The resilient modulus was (3650, 11030, 11600, and 11500) MPa under compression, tension, flexural and shear stresses respectively at optimum binder content. The permanent deformation under shear stresses is lower than that under tensile stresses by 16.8 %. On the other hand, the permanent deformation under compressive stresses is lower than that under flexure stresses by 89.4 %.