| The storage of iron tailings sand has caused serious pollution to the natural environment,and it is one of the urgent environmental problems to be solved in China If the iron tailings sand is reasonably applied in the project construction,it can not only solve the pollution problem caused by the iron tailings,but also save the amount of natural materials used in the project,meeting the needs of environmental protection and economy.At present,the secondary utilization of iron tailings by domestic and foreign scholars mainly focuses on cement concrete materials and road base mixture,and relatively little research on the application of iron tailings to asphalt surface layer.Brucite fiber is a kind of hydromagnetic fiber,which has been applied in cement concrete pavement engineering and achieved good benefits,but the application research on asphalt pavement is relatively few.Based on the regional characteristics of Zhangjiakou and the microscopic test analysis of raw materials,the water stability,low temperature crack resistance,high temperature stability and bonding properties of different types of brucite fiber-iron tailings sand asphalt mixtures are studied.According to the test results,use hierarchical analysis method to select the best brucite fiber-iron tailings sand asphalt mixtures are selected,and propose the engineering practice reference for the application of iron tailings sand and brucite fiber in asphalt pavement.The main research conclusions are as follows:（1）Iron tailings sand in Zhangjiakou have poor grading,which should be reasonably mixed before use.Under the same grade,the SiO2 content in iron tailings sand is 35.89%higher than limestone crumbs,with higher hardness and acidity,but relatively small specific surface area and more smooth texture.MgO and CaO in brucite fiber account for 69.04%of the total oxide,and the surface has strong alkali activity and large specific surface area,which is conducive to fiber adsorption of more asphalt.When iron tailings sand is used as aggregate,brucite fiber can be added to strengthen bonding properties.（2）With the increase of iron tailings sand content,the road performance of asphalt mixture is decreasing.The quality percentage of replacing limestone crumbs fine aggregate with iron tailings and with the same grading in the actual engineering shall be controlled within 0%～30%.（3）Adding brucite fiber with 0.3%and 0.4%can improve the road performance of iron tailings sand asphalt mixture,so the mixing amount of brucite fiber in actual engineering should be controlled within 0%～0.4%.After adding 0.4%brucite fiber,the residual Marshall stability of 30%iron tailings sand asphalt mixture increased by7.29%,the bending strain increased by 20.21%,the dynamic stability increased by16.91%,and the scattering loss decreased by 23.99%.The four indexes are better than other kinds of iron tailings sand asphalt mixtures.（4）30%iron tailings sand asphalt mixture mixed with 0.3%or 0.4%brucite fiber can replace ordinary asphalt mixture for road construction. |
