Experimental Study On Thermal Stability Of Asphalt Concrete Impermeable Layer

Asphalt concrete has good imperviousand strong defomation ability,and is widely used in impervious engineering.Asphalt concrete core wall and panel are commonly used imperviousstructures in water conservancy projects.After the project is put into operation,the asphalt concrete panel needs to be operated at high temperature,especially in summer.The surface temperature of the asphalt concrete impervious panel can sometimes reach more than 70℃,which is easy to produceflow deformation and slope flow.Therefore,the research on the high temperature performance of hydraulic asphalt concrete has gradually become a hot issue in the engineering field.In this paper,through the slope flow test of asphalt concrete with different mix ratio parameters under different influencing factors,the influence of different factors on the high temperature stability of asphalt concrete is explored,and the slope flow value prediction model with different mix ratio parameters is established.The main research contents are as follows:(1)Through the asphalt concrete slope flow test,the variation law of asphalt concrete slope flow value with test time under different conditions is explored.It is mainly divided into threestages:the slope flow value is almost linear growth stage;slope flow value gradually stable stage;slope flow value stable stage.(2)The influence of different mixture ratio parameters on the slope flow value of asphalt concrete is studied.The results show that the slope flow value decreases with the increase ofgradation index.Under the condition that the imperviousperformance can be guaranteed,the reasonable increase of gradation index will make the asphalt concrete have better high temperature stability.The slope flow value increases with the increase of filler content andbitumen aggregate ratio.When the filler content exceeds 13%,the increase of slope flow value is more obvious.In the selection of mix proportion,the filler content should not exceed 13%,and bitumen aggregate ratio should not exceed 7.2%.For asphalt concrete with the same mix ratio,the slope flow value with the maximum aggregate size of 16 mm is higher than that with the maximum aggregate size of 19 mm;asphalt type has a great influence on the slope flow value of asphalt concrete.The main influencing factor is the softening point of asphalt.As the softening point of asphalt increases,the slope flow value of asphalt concrete is smaller and the high temperature stability is stronger.(3)The influence of different mixture ratio parameters on the thermal stability of asphalt concrete is further explored,and the prediction model of slope flow value is established.The calculation model reflects the variation of slope flow value with different mixture ratio parameters with test time.The calculation results are in good agreement with the test results.(4)The grey correlation analysis was used to analyze the correlation between the six indexes of gradation index,bitumen aggregate ratio,filler content,softening point,test temperature and maximum aggregate particle size and the slope flow value.The correlation degree was ranked as test temperature>bitumen aggregate ratio>filler content>asphalt softening point>aggregate maximum particle size>gradation index.