| Moisture damage is one of the most common diseases of asphalt pavement.Generally,alkaline materials such as cement and lime are used as anti-stripping agents to enhance the adhesion between asphalt and aggregate and improve the moisture susceptibility of asphalt concrete.Steel slag powder has the potential to be used as an inorganic anti-stripping agent due to its high alkalinity,but there is currently no systematic in-depth research.In this paper,limestone filler,cement and slaked lime are used as reference samples,and the effect of steel slag powder on the moisture susceptibility of asphalt concrete was comparatively studied.Based on the analysis of basic physical and chemical properties of steel slag powder,the three major indexes,viscosity,rheological properties and heavy metal ion leaching concentration of the steel slag powder asphalt mortar were studied.The influence of the steel slag powder on the adhesion of asphalt and aggregate was quantitatively evaluated by using the image analysis technology,and the improvement mechanism of the adhesion was explored from the perspective of interface energy in combination with the surface energy theory.The Marshall stability test,the freeze-thaw split test under the conditions of the static and dynamic water,and the Hamburg rut test were used to study the effect of steel slag powder on the moisture susceptibility of asphalt concrete.Fatigue and creep performance of steel slag powder asphalt concrete were also investigated.The main research results are as follows:(1)After replacing limestone filler with steel slag powder,the consistency of asphalt is increased,the ductility of asphalt at low temperature is improved,and has a better "viscosity" effect on the asphalt;The leaching concentration of heavy metal ions such as Cd and Pb in the steel slag powder exceeds the upper limit of the surface water content of class III,but after being coated with asphalt,the leaching concentration of heavy metals in the steel slag powder asphalt mortar is below the upper limit.(2)The steel slag powder can obviously improve the adhesion of asphalt and aggregate.The improvement effect of steel slag powder on adhesion is better than that of cement but worse than of slaked lime,and its optimal content is 25%(volume ratio)of the total amount of filler.The Fe in steel slag powder has an adverse effect on adhesion,The Fe content should be less than 40%.The mechanism for improving the adhesion of alkaline fillers such as steel slag powder is to increase the surface energy of the asphalt mortar,result in an increase in the adhesion work and a decrease in spalling work between asphalt and acid aggregate.(3)The ratio of residual stability and freeze-thaw splitting residual strength of steel slag powder asphalt concrete under static and dynamic water conditions is higher than that of limestone filler asphalt concrete,and the number of rolling of Hamburg Rut Test is significantly improved.Part or even all of the steel slag powder replacement of limestone filler has the effect of improving water stability,but the effect is best at the 25% replacement amount.The effect of steel slag powder on the moisture susceptibility of asphalt concrete is better than that of cement but worse than that of slaked lime.The creep and fatigue performance of asphalt concrete specimens under water damage treatment conditions are better than those of limestone filler group.In summary,it is feasible that steel slag powder replaces part of the limestone powder as filler in asphalt concrete,and the best replacement amount is 25% of the volume of the limestone powder. |
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