Evaluation Of Adhesion Property Of Gneiss-Asphalt And Study On Road Performance Of Gneiss-Asphalt Mixture In Seasonal Freezing Region

With the expansion of transportation highway network and the improvement of environmental protection awareness in China,high-quality alkaline aggregates for highway construction are increasingly on the decrease.In Northwest China,gneiss and other acid aggregates have the advantages of wide distribution and rich reserves.However,acidic aggregates have poor adhesion to asphalt,which restricts its application in highway construction.Moreover,asphalt pavement is susceptible to environmental factors such as temperature,rain and driving loads,which is easy to produce loose and cracks diseases.Especially the climate of seasonal freezing region is characterized by low temperature in winter,large temperature difference between day and night,and serious freeze-thaw cycle,how to apply gneiss aggregates to highway engineering in seasonal freezing region with more severe environmental conditions has become the focus of many researchers.In this thesis,the silane coupling agent KH550 and the inorganic filler diatomite were used for composite modification,which improved the adhesion between gneiss aggregates and asphalt,and the road performance of gneiss asphalt mixture.Firstly,based on the theory of surface energy and mechanics,the effects of high viscosity SBS/rubber powder composite modified asphalt(CCR),modifier KH550 and diatomite on adhesion properties of between gneiss and asphalt were studied.The results show that compared with SBS modified asphalt,CCR composite modified asphalt has better adhesion to gneiss,and the improvement effect of modifier on between gneiss and asphalt adhesion is as follows: KH550/diatomite > KH550 > diatomite.Secondly,based on the grading theory of the series of stone asphalt concrete(SAC),four kinds of mineral gradation were designed for grading optimization(4.75 mm sieve pass rate is30%～40%).Through orthogonal experimental design method was used to study the significant effects of KH550,diatomite content and oil-stone ratio on Marshall test indicators and freeze-thaw splitting strength ratio,and the optimal ratio of KH550/diatomite composite modified asphalt mixture was determined by the comprehensive balance method.The results show that the SAC mineral gradation with 4.75 mm sieve pass rate of 34% is the optimal gradation.The optimal ratio of KH550-diatomite composite modified asphalt mixture is:KH550(0.9%),diatomite(7.5%),oil-stone ratio(5.8%).Thirdly,the effects of KH550,diatomite single modifier and KH550/diatomite compound modifiers on the road performance of gneiss asphalt mixture were systematically studied by dynamic modulus test,semi-circle bending test and freeze-thaw splitting test.The results show that KH550,diatomite and KH550/diatomite compound modifiers improve the high temperature deformation resistance,low temperature cracking resistance and water stability of gneiss asphalt mixture,and effect of compound modifiers was the best.Finally,the frost resistance of KH550/diatomite composite modified gneiss asphalt mixture was studied by porosity test and splitting test.The results show that KH550/diatomite compound modifier can enhance the adhesion between asphalt and gneiss aggregates,and reduce the freeze-thaw damage of the gneiss asphalt mixture.Logistic and GM(1,2)gray theory models can predict the porosity and splitting strength of gneiss asphalt mixture under freeze-thaw cycle condition.