Study On Low Temperature Crack Resistance Of Asphalt Materials Based On Relaxation Characteristics

Low temperature cracking is one of the main damage forms of asphalt pavement in cold areas.once it is not handled properly,it will cause other pavement diseases and cause economic losses.The main reason for low temperature cracking lies in the internal temperature stress caused by temperature change.when the temperature stress fails to dissipate in time and reach the limit that the pavement structure can bear,the pavement will crack.The behavior of pavement structure producing thermal stress and gradually dissipating stress is very similar to the stress relaxation phenomenon in rheology.Asphalt binder has an important influence on the low temperature performance of asphalt pavement.However,the research at home and abroad seldom combines the low temperature performance of asphalt binder with its stress relaxation characteristics,and does not put forward a test method for studying the stress relaxation characteristics of asphalt binder.Therefore,the relationship between stress relaxation ability and low temperature performance of asphalt materials is worthy of further study.In this chapter,the trabecular bending relaxation test is designed by dynamic mechanical analyzer(DMAQ800)to study the relaxation characteristics of different asphalts and their mortars,and the test parameters are optimized.The results show that the experimental parameters of low temperature relaxation should be 1% strain and 300 s test time.Through the test results,two relaxation performance indexes of asphalt materials are obtained: relaxation time and relaxation rate.According to the test results,it is found that the relaxation performance of asphalt materials is as follows: 90#asphalt > high viscosity asphalt(GN)> SBS modified asphalt(SBS)> rubber asphalt(XJ)> 50#asphalt.Through the comparison of the test results at different temperatures,it is found that the lower the ambient temperature,the worse the relaxation performance of asphalt materials.The relaxation performance of asphalt will be weakened after adding modifiers such as TPS,SBS and rubber powder.The frequency scanning and elastic recovery tests of 20 kinds of asphalt materials were carried out.the results showed that the addition of modifiers increased the elastic composition of asphalt materials and decreased their relaxation properties.After the mineral powder filler was added to the asphalt,it was found that it weakened the relaxation performance of the asphalt.The results of the two evaluation indexes are consistent,which can well evaluate the relaxation performance of asphalt materials,and the relaxation rate has more obvious distinguishing ability for asphalt materials.The low temperature performance of asphalt was studied based on low temperature bending rheological test(BBR),glass transition temperature test and asphalt unilateral notch beam bending test(SENB).The results show that through low temperature bending rheological test(BBR),the low temperature performance of asphalt materials is as follows: GN>SBS>XJ>90#asphalt >50#asphalt.Through the test,it is found that the addition of mineral powder increases the stiffness modulus of asphalt and reduces its creep rate,and the comprehensive compliance parameters obtained by analyzing the low temperature creep characteristics of asphalt by Burgers model are consistent with the above results;from the glass transition temperature test results,it can be seen that the glass transition temperature of asphalt material from low to high is: GN>SBS>XJ>90#asphalt>50#asphalt,and the low temperature performance of high viscosity asphalt is the best.And the glass transition temperature of asphalt mortar is higher than that of asphalt.The asphalt unilateral notched beam bending test(SENB)was introduced in this paper by which the fracture energy of asphalt material at low temperature and the maximum displacement of asphalt material was obtained.The test results show that the force-displacement curves of all kinds of asphalt materials are very different,and the order of fracture resistance of asphalt materials at low temperature is as follows: GN>SBS>XJ >90#asphalt >50#asphalt.Finally,the correlation between relaxation performance and low temperature performance of asphalt materials is analyzed by SPSS.The results show that the relaxation time and relaxation rate obtained from trabecular bending relaxation test are convenient and reliable for evaluating the relaxation performance of asphalt materials,and there is a significant correlation between relaxation performance and low temperature performance of asphalt materials,and there is a certain linear relationship.The relaxation performance index of asphalt material is modified by phase angle and elastic recovery rate,and the low temperature performance prediction equation is obtained by using the method of multiple linear regression analysis,and the low temperature performance evaluation of asphalt material based on relaxation characteristic is realized.