Comparative Research On Test And Evaluation Methods Of Low Temperature Performance For Asphalt Mixture

The low temperature performance of asphalt mixture reflects the low temperature crack resistance of asphalt pavement.Although there are a lot of test methods,due to the different test principles and evaluation indexes,there are greater differences in the test results.For this reason,based on the full-scale test loop track in Research Institute of Highway of Ministry of Transport(RIOHTrack),the thesis applied the four laboratory test methods,including low temperature trabecular bending,linear shrinkage coefficient,French trapezoidal beam and phase transformation,to carry out the comparative research on the low temperature performances of 23 kinds of asphalt mixture,in order to find the more scientific and reasonable test methods and evaluation indexes.(1)The strain energy at-10? was determined to be used as the recommended index for evaluating the low temperature performance of asphalt mixture by the low temperature trabecular bending tests at four temperatures.The tests of a new type of real-time temperature-strain acquisition system indicated that the linear shrinkage coefficient-temperature curve can reflect preferably the thermal shrinkage performance of asphalt mixture.The dynamic modulus tests of French trapezoidal beam were carried out to obtain the principal curves of complex modulus and phase angle when the temperature range was expanded.The results show that the principal curve of phase angle in 90?? is able to be used as the recommended index for evaluating the low temperature performance of asphalt mixture.(2)The effects of different factors on the low temperature performance of asphalt mixture were analyzed by means of various test evaluation indexes.The results show that the mixtures of SBS modified asphalt and AR rubber asphalt have the better low temperature performance,and the latter enhances with the increase of rubber powder content.But the low temperature performance of matrix asphalt mixture is poor,and it reduces with the decrease of asphalt grade.As for the mineral aggregate gradation,the results of the low temperature trabecular bending test show that the decrease of coarse aggregate content can improve the low temperature performance of asphalt mixture,but the results of the linear shrinkage coefficient test and the dynamic modulus test of French trapezoidal beam are opposite to it.It indicates that there are some contradictions in the evaluation results of different test models.(3)The glass transition temperature was introduced to evaluate the low temperature performance of asphalt mixture.It is found that all the glass transition temperature,the brittle point temperature of low temperature trabecular bending test and the peak point temperature of linear shrinkage coefficient-temperature curve are very close.(4)The principal component analysis and the correlation regression analysis were carried out between the different test indexes.The results show that the comprehensive correlation degree between the principal curve of phase angle and other indexes is maximum for the asphalt mixtures in upper and middle surface layer.Therefore,it is optimal to choose the dynamic modulus test of French trapezoidal beam and its principal curve of phase angle in 90?? as the test method and evaluation index of low temperature performance for the asphalt mixture in upper and middle surface layer.Similarly,it can be optimal to choose the low temperature trabecular bending test and its strain energy density as the test method and evaluation index of low temperature performance for the asphalt mixture in lower surface layer and flexible base.In summary,the results of this thesis can provide a scientific reference for the reasonable evaluation of low temperature performance of asphalt mixture.