rutting resistance evaluation of large stone asphalt mixtures

rutting of hot mix asphalt pavements due to increased number of heavy vehicles, especially in tropical regions, causes several performance problems. large stone asphalt mixtures have more stiffness and shear resistance and so more rutting resistance compared to conventional mixtures. hence, using these mixtures in thick layers of hot mix asphalt pavements at tropical regions could be an appropriate option for asphalt mix design. large stone asphalt mix (lsam) is a mixture with the nominal maximum aggregate size between 25 and 63 mm. modified marshall mix design method according to astm-d5581 is used to design these mixtures. in this laboratory research, the rutting resistance of lsam mixtures is evaluated and compared to conventional hma mixtures. large stone asphalt mixtures were designed with four different aggregate gradations as well as a conventional dense graded mixture. rutting test specimens prepared at four different asphalt contents for large stone asphalt mixtures and at optimum asphalt content for the conventional mixture. the rut depth of specimens at 60°c determined using hamburg wheel tracking device after 12000 loading cycles. the data obtained from mix design and rutting tests analyzed using spss statistic software and the effects of various parameters such as asphalt content, air voids of compacted asphalt mixture and gradation on the rutting resistance of large stone asphalt mixtures were evaluated. at the end, a mathematical model presented for predicting the rut depth of large stone asphalt mixtures.