Research On Expansion Inhibition Method Of Steel Slag And Pavement Performance Of Asphalt Mixture

Steel slag is an accessory product of steelmaking and also an industrial waste slag.A large number of steel slag is piled up in the open space,wasting land resources,but also cause serious pollution to the environment.When steel slag is added into asphalt mixture instead of some natural ore,it can effectively reduce the consumption of natural stone,and is also an important way to solve the environmental pollution caused by steel slag.Due to the large amount of free calcium oxide in steel slag,hydration reaction occurs after it encounters water,which increases the volume of active material of steel slag by nearly 100%.Therefore,steel slag has potential expansion damage in the application of road engineering.In view of this,this study prepared hydrophobic modified paint with acrylic emulsion and cement to treat steel slag with hydrophobic,and evaluated the improvement of the swelling of steel slag by the surface modification method through the study of the basic properties of modified steel slag.Based on this,the influence of different modified steel slag content on asphalt pavement performance was studied,in order to promote the efficient utilization of steel slag in road engineering.Firstly,aiming at the problem of steel slag expansibility,polymer cement waterproof coating was selected as the surface hydrophobic modification of steel slag,and the improvement of the basic properties of steel slag was evaluated through the tests of the modified steel slag’s soaking expansion rate,water absorption rate,high temperature stability and adhesion to asphalt.The results show that the polymer cement waterproof coating can form a dense hydrophobic film on the surface of steel slag,and prevent the contact between water and steel slag,so as to inhibit the expansion of steel slag,and when the ratio of cement to cement is 1:1.4,the final impregnation expansion rate of modified steel slag reaches the minimum.The surface of steel slag samples was observed by X-ray energy dispersive spectroscopy(EDS)and scanning electron microscopy(SEM)to reveal the changes of morphology and chemical composition before and after modification.The results show that the hydrophobic coating can effectively fill the micropore and cracks on the surface of steel slag and reduce the content of active substances on the surface of steel slag.Subsequently,the optimal ratio of five kinds of steel slag asphalt mixtures with different amounts of modified steel slag was determined by volume replacement method.The results show that the optimum ratio of asphalt mixture with modified steel slag content of 0% to 100% is 4.9%,5.0%,5.2%,5.3%,respectively.Then,the influence of steel slag content on the water stability of asphalt mixture was analyzed by volume stability test,immersion Marshall test and freeze-thaw splitting test.The results show that the water damage resistance of modified steel slag asphalt mixture is better than that of ordinary steel slag asphalt mixture,but it is still less than that of basalt asphalt mixture.High temperature stability of steel slag asphalt mixture was studied by high temperature rut test.The results show that the dynamic stability of asphalt mixture reaches the highest value when steel slag content is 50%,that is,steel slag can effectively restrain the high temperature disease of asphalt pavement.In addition,different steel slag content,steel slag modification or not has no significant improvement on the low temperature cracking resistance of asphalt mixture.The sliding resistance of modified steel slag asphalt mixture was tested and analyzed by a tilting friction coefficient tester.Combined with the tire-pavement dynamic friction test system(TDFA)independently developed by our research group,the decay trend of sliding resistance of modified steel slag asphalt mixture was analyzed.The results show that,compared with the basaltic asphalt mixture,after surface modification treatment,the anti-sliding value and friction coefficient of the asphalt mixture are significantly increased,and with the increase of the content of modified steel slag aggregate,the friction coefficient shows an overall upward trend.During the whole abrasion cycle,because the wear resistance of steel slag is better than that of basalt aggregate,the decay rate of its friction coefficient is significantly reduced compared with that of basalt asphalt mixture,which indicates that the steel slag asphalt mixture has good skid resistance and durability.The above research results provide certain test data and construction basis for the popularization of this kind of green environmental asphalt pavement,which has certain economic,social and environmental benefits.