Effects of styrene-butadiene-styrene on stiffness of asphalt concrete at different traffic conditions

The previous studies have explored the effects of styrene-butadiene-styrene (sbs) as the most prevalent modifier for asphalt mixtures. the current study intends to compare stiffness modulus of control and sbs modified asphalt mixtures under different traffic loadings. to this end,resilient modulus tests were performed on both conventional and sbs modified specimens. tests were conducted at 5,25 and 40°c with loading times of 50,100,300,600 and 1000 milliseconds and 4,9 and 30 as ratio of rest periods (between loading pulses) to loading times (r/l). using these test parameters and haversine and square loading pulses that represent vertical stress distribution at different depths within an asphalt layer,a variety of traffic densities and vehicle speeds were simulated and their effects on stiffness of asphalt concrete were determined. results indicated that sbs modification provide higher stiffness under haversine pulse with long loading time at 40°c,so that it was about 3 times of unmodified mixture stiffness. the effect of traffic density that represented by r/l was significant only in long loading time (1000 ms) especially under haversine pulse. © school of engineering,taylor’s university,all rights reserved.