Experimental Study On Performance Of Asphalt Mixture Strengthened By Coarse Recycled Concrete Aggregate

With the rapid development of infrastructure construction in our country,there is an increasing shortage of high-quality natural stone.At the same time,the output of construction waste increases year by year.How to dispose and use these construction waste has become a topic of concern.Applying recycled aggregate prepared from waste concrete to asphalt mixture can reduce the cost of road construction and save natural aggregate,which is a new way to utilize construction waste resources at present.The quality of recycled coarse aggregate produced by simple crushing is low,and it is difficult to meet the construction technical requirements of asphalt pavement.Therefore,in this paper,different methods are used to strengthen the recycled coarse aggregate,and the performance of the recycled coarse aggregate asphalt mixture before and after strengthening is tested.Firstly,the differences of physical and mechanical properties between natural limestone coarse aggregate and old cement concrete recycled coarse aggregate are studied.It is found that the surface mortar of recycled coarse aggregate has high adhesion,low apparent relative density,high water absorption and large crushing value,and its properties are obviously inferior to those of natural coarse aggregate,and its variability is large.Secondly,two methods of physical(high temperature mechanical grinding)and chemical(TEOS solution infiltration)are used to strengthen the recycled coarse aggregate from two aspects of removing mortar and improving the surface characteristics of mortar.According to the different influencing factors,9 groups of test schemes are designed to test the performance indexes of the recycled coarse aggregate after each scheme is strengthened.Combined with the analysis of micro characteristics,the comprehensive analysis is carried out After the evaluation,the combination of high temperature and mechanical grinding at 400℃+500 ram revolutions is selected as the strengthening scheme of recycled coarse aggregate in this paper.Then,the Marshall test method was used to design the mix ratio of 7 kinds of asphalt mixtures with different blending amounts(0%,15%,30%,45%)before and after the strengthening of recycled coarse aggregate.The results show that with the increase in the amount of recycled coarse aggregate,the oil-rock ratio of the mixture increases,the relative density of the gross volume and the maximum theoretical relative density decrease,the stability decreases,the flow value increases,after high temperature-mechanical grinding The oil-rock ratio of recycled coarse aggregate asphalt mixture has decreased.Finally,the high temperature stability,low temperature crack resistance,water stability,fatigue resistance and crack resistance of recycled coarse aggregate asphalt mixture before and after strengthening were tested by high temperature rutting test,small beam bending test,immersion Marshall test,freeze-thaw splitting test,four point bending fatigue test and ideal-ct test,respectively,and compared with natural bone A comparative study of asphalt mixture.The results show that the addition of recycled coarse aggregate can improve the high-temperature stability of asphalt mixture to a certain extent,which has a negative impact on other properties;high temperature mechanical grinding can improve the low-temperature crack resistance,water stability and mechanical properties of recycled coarse aggregate asphalt mixture.When the content of recycled coarse aggregate is controlled below 30%,the performance of the asphalt mixture can meet the requirements of the specification,and it can be improved by an appropriate amount after strengthening.The research results in this paper provide a reference for the reinforcement of recycled coarse aggregate and its application in asphalt mixtures,and have certain research significance and application value.