| Road transportation plays an important role in the transportation system.At present,the road maintenance mileage in our country has exceeded 5 million kilometers,accounting for more than 99.0% of the total road mileage.The huge road maintenance mileage has a huge demand for high-quality road engineering aggregates.The shortage of natural aggregates is becoming more and more serious,and the maintenance work is facing enormous pressure and challenges.On the other hand,steel slag is a solid waste generated during the steelmaking process.Due to the huge output of steel slag,and its accumulation and landfill are easy to cause harm to the environment,many countries have regarded the recycling of steel slag as one of the strategies for sustainable development.The accumulative stockpile of steel slag in our country exceeds 1 billion tons,but the comprehensive utilization rate is less than 30%.It is urgent to explore reasonable utilization methods to develop the recycling value of steel slag.For the resource dilemmas faced by pavement maintenance and the environmental dilemmas faced by steel slag,this study firstly explored the physical and chemical properties of steel slag,and prepared steel slag-based thin overlay,micro-surfacing and chip seal maintenance materials.Then,the advantages of steel slag over natural aggregate in terms of morphology,wear resistance,adhesion to asphalt,and chemical composition were investigated.The internal skeleton structure characteristics,hydrodynamic damage,surface texture,and functional characteristics of steel slag-based maintenance materials were explored,and the enhancement effect and reasons of steel slag on maintenance materials were clarified.The following conclusions were obtained:(1)The rich angular characteristics of steel slag help to increase the number of contact points in the skeleton structure,while the deviated spherical shape and rough surface can increase the contact length.Under the coupling effect of the two effects,the replacement of natural aggregate by steel slag can significantly increase the comprehensive contact index and skeleton quality in the meso-skeleton structure of the maintenance material,thereby improving the service performance.(2)The attenuation of mechanical properties and internal structure of steel slag-based maintenance materials before and after hydrodynamic damage is lower than that of traditional maintenance materials,indicating that steel slag replacing basalt coarse aggregate can enhance the structural stability of maintenance materials.The use of silicone resin to modify the surface of the steel slag can fill the micro-cracks and residual pores on the surface of the steel slag,and isolate the contact between the water and the steel slag,thereby enhancing the resistance to hydrodynamic damage of the steel slag-based maintenance materials.(3)Replacing natural aggregates with steel slag significantly improves the skid reisistance of steel slag-based maintenance materials.Steel slag increases the number of asperities and sharpness of peaks on the sample surface.When the tire is in contact with the surface of the slag-based maintenance materials,more asperities and spikes will cause micro-cutting,effectively increasing the frictional resistance on the contact surface.The enhancement effect of steel slag on texture is mainly due to the excellent wear resistance,rich angular features and irregular shape.(4)With a reasonable amount of steel fibers,the steel slag helps to improve the induction heating and microwave thermal induction effects of the chip seal,thereby enhancing the flow characteristics of the asphalt.This makes the inter-molecular interdiffusion of the asphalt where the interfacial strength is damaged spontaneously,so that the aggregate to be exfoliated is tightly bound to the asphalt again due to the diffusion and wetting of the asphalt. |
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