The Research Of Viscoelastic Fatigue Damage Properties Of Fine Steel Slag Asphalt Mortar

As a kind of industrial waste,steel slag has low utilization rate and large amount of hoarding in China,but it is similar to natural aggregate in mechanical properties.It is a kind of potential road material.Applying steel slag to asphalt concrete can not only solve the problem of steel slag hoarding but also alleviate the environmental damage caused by the mining of natural stone.In asphalt pavement,the problem of fatigue damage has been one of the most important problems in the damage of asphalt pavement,and it has been a hot research topic for road engineering researchers for a long time.Because of the viscoelastic characteristics of asphalt concrete,the traditional research method is difficult to effectively reflect the fatigue damage performance,and there are some limitations on the study of the fatigue damage of asphalt concrete.In order to study the effect of steel slag replacing natural aggregate on the performance of asphalt concrete,the fatigue damage performance of asphalt concrete after replacing natural aggregate with steel slag is studied in this paper.The main work and conclusion are as follows:(1)According to the design of Marshall design method,the mixture ratio of the steel slag and concrete is designed according to the relative density of the volume of the aggregate and the equal volume method.Because of the porosity of steel slag,in order to calculate the asphalt absorption coefficient C and the maximum relative density of the steel slag asphalt concrete,the asphalt impregnation method is used to test the effective density of the steel slag mixture.(2)The performance of steel slag asphalt concrete and limestone asphalt concrete is studied,including stability,residual stability,freeze-thaw cycle and high temperature rutting performance.The water resistance and high temperature performance of two kinds of asphalt concrete are studied,and the energy absorption and release capacity of two kinds of asphalt concrete are discussed according to the function transformation.The results show that the energy absorption capacity of the steel slag asphalt concrete is greater than the limestone asphalt concrete,and the steel slag asphalt concrete is superior to the limestone bituminous concrete in the water resistance damage and the high temperature deformation resistance.(3)In view of the fatigue problem of steel slag asphalt concrete,the fatigue performance of steel slag asphalt concrete is studied by indirect tensile fatigue test and digital image correlation(DIC).method The results show that the fatigue life of steel slag asphalt concrete has been greatly improved under the same test conditions,and the effect of steel slag replacing fine aggregate is the most significant.(4)In order to further study the influence of steel slag on fatigue performance of asphalt concrete.In this paper,the influence of coarse aggregate on fatigue performance is eliminated based on the original AC-13 mixture ratio,and steel slag asphalt mortar is used as the research phase.After eliminating the influence of coarse aggregate,the asphalt consumption of asphalt mortar is calculated according to the original AC-13 asphalt content,specific surface area and coarse aggregate passing percentage.The dynamic modulus and phase angle of steel slag asphalt mortar were tested and the viscoelastic parameters were determined.The results show that the deformation resistance of steel slag asphalt mortar is higher than that of limestone asphalt mortar at high frequency and low frequency.(5)Due to the traditional fatigue damage research method,it is difficult to effectively reflect the fatigue damage of asphalt concrete.In this paper,the theoretical framework of simplified viscoelastic continuous damage model(S-VECD model)based on material constitutive relation is reviewed and analyzed.The fatigue damage evolution performance of steel slag asphalt mortar based on S-VECD model is studied by direct tensile fatigue test,and the effect of test temperature and strain amplitude on the S-VECD model is analyzed.The fatigue damage definition method and fatigue damage evolution process of steel slag asphalt mortar are analyzed and studied.The results show that the S-VECD model is independent of the test temperature and strain amplitude in the fatigue damage evolution test of asphalt mortar,and the damage characteristic curve of different materials(C-S curve)is the only one,and the fatigue damage performance of the steel slag asphalt mortar is superior to the limestone asphalt concrete,and the S-VECD model is special to the fatigue damage of the asphalt mortar.The evaluation of the sign is feasible.During the whole process of damage,the change of modulus and energy of asphalt mortar is divided into three stages: the stage of damage initiation,the stage of damage steady growth,and the stage of damage and instability.