Experimental Study On Low-Temperature Crack Resistance Of Asphalt Mixture In Alpine Grassland Of Northeastern Inner Mongolia

One of the typical diseases of asphalt pavements is cracking,and pavement cracks exist widely.Building highway in the alpine steppe region of northeastern Inner Mongolia,there will appear cracks in the asphalt pavements under low temperature conditions.It is of great engineering value to study the low-temperature anti-cracking performance of asphalt mixture,in order to improve the low-temperature anti-cracking performance of the pavements and prolong the service life of the asphalt pavements.The main contents and achievements of this thesis are as follows:(1)After analysing the methods used to evaluate the low-temperature anti-cracking performance of asphalt mixtures at home and abroad and combining the climatic characteristics of the alpine steppe region in the northeastern Inner Mongolia,it was determined that the low-temperature bending test,indirect tensile creep test(IDT)and thermal stress restrained specimen test(TSRST)were used to evaluate the low-temperature anti-cracking performance of asphalt mixtures in this thesis.(2)After the performance of the raw material was measured,the mix proportion of five kinds of AC-13 asphalt mixtures and three kinds of AC-20 asphalt mixtures was obtained by Marshall mix proportion design method.The water stability and high-temperature stability were verified to ensure that the determined mix proportion of asphalt mixture meet the requirements.(3)Low-temperature bending tests of eight asphalt mixtures under three temperatures of 0℃,-10℃,and-20℃ are carried out.It is concluded that the influence of mineral aggregate gradation on the low-temperature anti-cracking performance of asphalt mixture is not significant.The improvement of the low-temperature anti-crack performance of asphalt mixtures is more significant between rubber asphalt and extremely cold asphalt than SBS modified asphalt and SBR modified asphalt.(4)The indirect tensile creep tests were carried out at three temperatures of 0℃,-10℃and-20℃,and the indirect tensile creep data of eight kinds of asphalt mixtures were measured.The creep compliances were calculated by the power function model.Then,based on the time-temperature equivalence principle,the creep compliance master curves(CCMC)of eight kinds of asphalt mixtures were established at the reference temperature(-10℃).The results show that the power function model can characterize the indirect tensile creep compliance curve of asphalt mixtures well.(5)The thermal stress restrained specimen tests of eight kinds of asphalt mixtures were carried out,and the temperature-stress curves were drawn to obtain the failure parameters of eight kinds of asphalt mixtures.The effects of gradation types,asphalt type and cooling rates on the low-temperature anti-cracking performance of asphalt mixtures were analyzed.The results show that the gradation types and cooling rates have little effect on the low-temperature anti-cracking performance.(6)It is found that there is a good correlation between the failure temperatures,the flexural strains at-10℃ and the failure strengthes of the eight asphalt mixtures.The proportion of mineral powder has the greatest influence on the low-temperature anti-cracking performance of asphalt mixtures with the same type of asphalt mixture and different aggregate gradations.In the aggregate,9.5mm ~ 16 mm of the coarse aggregate have the greatest influence,and 2.36 mm ~ 4.75 mm the smallest.In addition,the asphalt density has the greatest influence on the low-emperature anti-cracking performance of asphalt mixtures,while the penetration index has the least influence.