Research On The Volumetric Property Of Asphalt Mixture

Marshall method of mix design is still the design method of asphalt mix in China currently .The optimum asphalt content (OAC) is the essence of proportion design of asphalt mixture. The testing and computation method of volumetric property mainly influencing factors on the OAC of asphalt mixture and the relationship among different methods determining the OAC are studied by experimental statistics method.Test statistics results show,no statistically significance difference in testing variability was observed between results of SSD method and paraffined method and that statistically significance difference in testing bulk density is observed between two methods .The water absorption and mixture type interaction, the air voids and mixture types interactions are significant, therefore the single factor can not evaluate the adaptability of SSD method reliably.The accuracy of the theoretical maximum specific gravity of polymer modified asphalt mixture by vacuum test method and by computation method are studied. Vacuum test method does not hold good for measuring theoretical maximum specific gravity of polymer modified asphalt mixture and SMA . The theoretical maximum specific gravity should be gained by theoretical computation methodThe 4 kinds of computation methods of volumetric property of asphalt mix are compared and analyzed. According to computation method in the specifications of our country ,the VMA and VFA are greater and air voids is smaller than that using American method.Blows tests shows,the changeable value of OAC is about 0.2%-0.3% when the blows number from 75 to 100. The changeable values are the same as that of different Marshall index .It is suggested adjusting the scope of volumetric property and keeping the hammer blows of 75.The OAC of Marshall mix design method and Superpave mix design method is statistically significance difference according to the result of T testing. The OAC of Marshall is greater than that of Superpave. The influence of aggregate gradation type on OAC differences of each mixture is significant , the influences of the other factors are very small .