Detecting the Additives Impact on The Durability of Asphalt Concrete

Abstract

Modification of asphalt cement with additives is considered as a sustainable issue to enhance the asphalt concrete quality and durability among the expected service life. An attempt has been made in the present investigation to detect the influence of modification of the asphalt binder by 2 % silica fumes and 4 % fly ash additives on the durability of asphalt concrete in terms of fatigue life under long-term ageing and moisture damage.  Asphalt concrete wearing course mixtures have been prepared and compacted by roller in the laboratory. The beam specimens of 400 mm length and 50 mm height and 63 mm width were extracted from the slab samples. The beam specimens were subjected to the four-point repeated flexural bending beam test. The test was terminated when the beam has reached a 50 percent reduction in stiffness. The fatigue life was monitored in terms the number of load repetitions to reach the failure under three constant micro strain levels of (250, 400, and 750). The reduction in fatigue life after long-term ageing for control, silica fumes modified, and fly ash modified mixtures was (74.7, 38.4, and 60) %, (66.2, 52.4, and 64.3) %, (63.9, 63.1, and 57.5) % under 250, 400, and 750 microstrain levels respectively. However, the reduction in fatigue life after practicing moisture damage as compared to the fatigue life before such process for control, silica fumes modified, and fly ash modified mixtures was (71.2, 59.6, and 37.2) %, (37.1, 64.9, and 11.2) %, (71, 84.8, and 32.2) % under 250, 400, and 750 microstrain levels respectively. It was concluded that Fly ash modified mixture exhibit lower susceptibility to long-term ageing process as compared to other mixtures, while silica fumes modified mixture exhibit lower susceptibility to moisture damage as compared to other mixtures.