Evaluating Performance Of Bio-asphalt And Rock-asphalt Composite Modified Asphalt Binder

Asphalt binder is one of the main building materials for road engineering.Conventional petroleum asphalt is an auxiliary product in the process of fractionating crude oil.Due to the continuous decline of oil reserves,the price of petroleum asphal t has been at a high level for a long time.It is urgent to look for new green materials to reduce the use of petroleum asphalt,even more replace petroleum asphalt.As a new road material,bio-asphalt is renewable,green,wide-ranging and low-cost,which has attracted more and more scholars' attention.However,its defects such as insufficient high temperature stability restrict the further use of bio-asphalt..Besides,As rock asphalt significantly improves the high temperature performance of asphalt,rock asphalt modification technology tends to be mature and has been widely used in various parts of the world,which is expected to make up for the shortage of bio-asphalt.In this paper,bio-asphalt and rock asphalt are blended as a composite modifier into penetration 70 base asphalt to prepare composite modified asphalt with the composite modifier ranges from 0% to 60%.Based on the conventional penetration tests evaluating system and American Superpave evaluation method,the effect of composite modifier on the performance of asphalt was discussed in the form of laboratory tests.Firstly,the ratio of rock asphalt to bio-asphalt is determined by ensuring that the different modified composite asphalts have the same 25 °C penetration as the base asphalt.According to the conventional penetration evaluation system,the penetration,softening point and ductility of original and RTFO aged composite modified asphalt were tested.The test results show that with the increasing of composite modifier,the high temperature performance and temperature susceptabilty are continuously improved,and the anti-aging performance is also improved,but its low temperature ductility is insufficient.Secondly,according to Superpave asphalt evaluation system,the rheological properties of asphalt were analyzed through rotational viscosity,DSR and BBR tests,and the performance graded of composite modified asphalt was carried out.The results show that with the increasing of composite modifier,the viscosity increases,the high temperature performance and the temperature susceptabilty are improved,which is similar to conventional penetration evaluation system.The low temperature performance is improved when a small amount of the composite modifier is added,but then it decreases continuously,and when the amount is more than 40%,the low temperature performance is lower than that of the base asphalt.Finally,the correlation between the conventional and rheological properties of the composite modified asphalt was analyzed.The results show that although the regression equation between the conventional and rheological properties of different modified asphalts is difficult to unify,there is a significant correlation for composite modified asphalt in terms of high temperature performance,low temperature performance,serviceable temperature range and temperature susceptabilty.