| With the continuous expansion of transportation infrastructure construction,the shortage of sand and stone materials is becoming more and more serious.Therefore,it is urgent to seek efficient and feasible alternative materials for pavement engineering.Iron tailings is a kind of industrial solid waste containing a large amount of fine granular material.Therefore,the application of iron tailings in pavement construction can not only alleviate the shortage of sand and stone materials,but also improve the utilization rate of iron tailings and solve the environmental and safety problems,which has significant environmental protection and economic benefits.Therefore,this study explores the applicability of iron tailings in asphalt pavement according to the logic of raw material property-mortar property-mixed roading-rut test simulation.In order to study the feasibility of iron tailings as fine aggregate of asphalt mixture,this study first tested the basic properties of iron tailings from a macro perspective,including density,water absorption,particle size composition,needle flake content,crushing value and wear value.Subsequently,X-ray fluorescence spectrometer(XRF)test was used to test its chemical composition from the microscopic point of view,X-ray diffractometer(XRD)test was used to characterize its phase composition,and scanning electron microscope(SEM)test was used to observe its apparent morphology.The results show that iron tailings have the physical and chemical basis and mechanical properties to replace the fine aggregate of asphalt mixture.Secondly,based on the scale of asphalt mortar,the adhesion of iron tailings asphalt mortar was studied by improved boiling test and drawing test.According to the improved boiling test,it is found that the adhesion grade of six kinds of asphalt mortar composed of three aggregates of iron tailings,limestone and basalt,SBS modified asphalt and 70 # matrix asphalt is 5.In this study,the pull-out force values required for the failure of specimens with different freezing time were also measured by the improved pull-out test to quantitatively characterize the adhesion of various types of asphalt mortar.Based on the grey correlation analysis method,the effects of physical and chemical indexes and basic characteristics of iron tailings on the adhesion of asphalt mortar were studied.The results showed that the order of influence of various factors on the adhesion of asphalt mortar was apparent density >apparent morphology > Ca O * Mg O content > albite content.Then,based on the scale of asphalt mixture,this study first studied the optimal gradation of iron tailings asphalt mixture,and used 70 # matrix asphalt and SBS modified asphalt to prepare three asphalt mixture specimens with different iron tailings content.Subsequently,its road performance was evaluated by high temperature stability,water stability and low temperature crack resistance test.At the same time,the optimal dosage of iron tailings in iron tailings asphalt mixture was determined by linear weight method and analytic hierarchy process.The results show that the optimum content of iron tailings in 70 # matrix asphalt mixture is 59.1% of the total mass of fine aggregate,while the optimum content of iron tailings in SBS modified asphalt mixture is 75.5% of the total mass of fine aggregate.Finally,combined with the scale of asphalt mortar and asphalt mixture,the viscoelastic parameters of iron tailings asphalt mixture specimens were obtained by creep test.Based on the time hardening model,the material parameters of iron tailings asphalt mixture were determined,and a three-dimensional rutting prediction model was established.The results show that the error between the measured deformation and the predicted deformation of the simulation model is within 7%.The model established in this thesis has high reliability,and the appropriate amount of iron tailings can improve the high temperature performance of asphalt mixture. |
