The Research On Low-temperature Cracking Of Asphalt Pavement Based On Stress Relaxation Effect Of Aged Asphalt Mixture

The low-temperature cracking of asphalt pavement is a very common problem at home and abroad, it has an important relation with tensile strength, relaxation property and shrinkage characteristic of the asphalt concrete. Among all these factors, the stress relaxation property of the material is the basic reason, which leads to the low-temperature cracking of asphalt pavement. With aging process of the asphalt, the stress relaxation ability of asphalt pavement decreased, so the Low Temperature Anti- cracking Performance decreased rapidly.Through stress relaxation test at experimental condition of different temperature and different aging degree of asphalt mixture of AC-13C, Relaxation modulus master curves of asphalt mixture were obtained according to time-temperature equivalence principle and W. L. F. equation. Then these curves were fitted by different viscoelastic models, and the six-units generalized Maxwell model was recommend to Characterize asphalt mixture relaxation property.Then Parameters of the viscoelastic model of asphalt mixture at different aging degree was obtained by nonlinear regression.According to the result of the stress relaxation test of asphalt mixture at different aging degree, and based on the Free-Volume-Theory of material viscidity, the relation between aging and temperature of asphalt mixture is deduced, which shows that the aging relaxation modulus can be replaced by the non-aging at the lower temperature state.According to the thermal stresses formulas of asphalt pavement of stress relaxation effect considered during the cooling process and aiming at asphalt pavement of different aging degree, the thermal stress under different kinds of cooling rate was calculated .The results showed that with aging degree increase, because of relaxation ability of asphalt pavement decrease and its stiffness modulus increase, thermal stresses rose rapidly. Tensile Strength of asphalt mixture at different temperature and different aging degree was obtained through direct tension test. The method of the cracking temperature prediction was determined according to the relation between thermal stresses of asphalt pavement and Tensile strength at corresponding temperature condition. And also the cracking temperature of asphalt pavement of different aging degree under the cooling rate ofδ= -10℃/h was predicted. The result shows that aging of asphalt plays an important role in the low-temperature cracking of asphalt pavement, the higher the aging degree, the higher the temperature of low-temperature cracking of asphalt pavement, and it is more likely to produced low-temperature crack.