Study On Preparation And Properties Of USP Modified Asphalt And Mixture For Cold Repair

Solvent type cold mix asphalt mixture has the advantages of low cost,little environmental impact and convenient for construction.It is a common material in pavement pothole repair engineering.Researchers have done a lot of research and achieved some progresses.However,it still has many problems,such as poor water stability and crack initiation at low temperature.Besides,the diluent is generally diesel or gasoline,which can not better meet the requirements of economic and environmental protection.Therefore,the original asphalt was modified by USP(U-Usual Temperature,S-Synthetic Rubber,P-Pitch)low temperature modifier in this study.The environmental friendly solvent biodiesel was selected as the diluent.A certain amount of normal temperature tackifier and new environmental protection non-amine anti-stripping agent were added to improve the performance of cold patching asphalt.Its aim is to obtain a new environmental protection high-performance cold mix asphalt mixture which can be widely used in pothole repair.Firstly,this paper determined the range of each material content by single factor test,and carried on the orthogonal test to each material according to the test result,Five cold supplementary asphalt schemes(scheme 0,1,2,9,13)were preliminarily selected by visual analysis and variance analysisSecondly,the performance tests of cold patching asphalt were carried out,According to the test results,scheme 1 and scheme 2 were determined as the distribution ratio of cold patching asphalt.The high temperature dynamic shear test(DSR)and low temperature rheological test(BBR)were carried out for the two schemes.Test results show that the complex modulus of scheme 1 and scheme 2 are 1.08kPa and 1.03kPa respectively at 70℃.Both of their stiffness modulus are less than 300 MPa and their creep rate are greater than 0.3 at-24℃,which indicates that the cold patching asphalts of the two schemes have better high temperature and low temperature properties.The microscopic researches of cold patched asphalt show that the components of cold patched asphalt can be dissolved and reacted well.The reaction process is a complex process of physical and chemical modification.Then,the mix proportion design of cold mix asphalt mixture was conducted,mainly including the determination of gradation type and the optimum asphalt content.In this research,the LB-13 gradation was used,and the gradation was tested by the Bailey method.The optimum asphalt content of cold mix asphalt mixture was determined to be 5.5%by empirical and experimental methods.The composite fiber composed of basalt fiber and polyester fiber was used to improve the performance of cold mix asphalt mixture.Taking Marshall stability as the index,the ratio of basalt fiber to polyester fiber was determined to be 2:3.Finally,the performance tests and benefit analysis of cold mix asphalt mixture were carried out.The cold mix asphalt mixture prepared by cold patching asphalt in scheme 1 and scheme 2 were studied to analyze the influence of composite fiber with different content on the performance of cold mix asphalt mixture.The results show that the cold mix asphalt mixture prepared by scheme 2 cold patching asphalt(the ratio of modifier,diluent,anti stripping agent and tackifier was 6:20:0.4:8 respectively)has better road performance.The performance improvement of cold mix asphalt mixture is the best and with better storage stability,economic and social benefits when the content of composite fiber is 0.4%.