Study On Self-healing Performance And Molecular Dynamics Simulation Of Steel Slag Powder Modified Asphalt Mastic

Steel slag is one of the solid waste generated in industrial steelmaking,with a huge output,accounting for 10% to 15% of the total amount of steel.In recent years,China’s steel industry has developed rapidly,and the accumulated amount of steel slag has also increased rapidly.If not treated in a timely and effective manner,steel slag will occupy a large amount of land resources and pollute the surrounding environment.Under the requirements of environmental protection policies such as "carbon neutrality" and "carbon peaking",it is very necessary and urgent to select appropriate utilization ways and treatment processes to improve the utilization rate of steel slag.Research has found that the application of steel slag as aggregate in road engineering not only effectively improves the utilization rate of steel slag,but also improves the road performance of asphalt mixtures.To study the self-healing performance and modification mechanism of steel slag powder modified asphalt mastic,this thesis uses steel slag powder with a particle size less than 0.075 mm to replace some limestone powder to prepare steel slag powder modified asphalt mastic.By analyzing its microscopic properties and rheological properties,the most obvious modification effect in steel slag powder modified asphalt mastic was determined as the replacement of limestone powder with steel slag powder.Select the steel slag powder with the most obvious modification effect to replace the amount of limestone powder to prepare asphalt mastic.Using limestone powder asphalt mastic as the reference group,complete linear amplitude scanning self-healing test and fluorescence microscopic analysis self-healing test,analyze the self-healing performance and modification mechanism of steel slag powder modified asphalt mastic,and use molecular dynamics simulation method to describe the diffusion characteristics of asphalt molecules during the self-healing process of asphalt mastic at a nanoscale.This thesis designs 5 types of steel slag powder as substitutes for limestone powder(0%,10%,20%,30%,50%),and uses 70 # base asphalt and SBS modified asphalt to prepare steel slag powder modified asphalt mastic(steel slag powder modified base asphalt mastic,SMBAM;steel slag powder modified SBS asphalt mastic,SMSAM).The microstructure,high-temperature stability,and rheological properties of steel slag powder modified asphalt slurry were analyzed through Fourier transform infrared spectroscopy(FTIR),thermogravimetric analysis(TGA),multiple stress creep recovery test(MSCR),and temperature scanning test.The results indicate that when steel slag powder replaces some limestone powder to prepare asphalt mastic,new chemical functional groups will not be generated in the asphalt mastic,but the number of some existing functional groups can be changed.Moreover,steel slag powder has a relatively small impact on the high-temperature stability of asphalt mastic,with SMSAM having lower stress and temperature sensitivity than SMBAM.However,the modification effect of SMBAM is better than that of SMSAM.Based on the results of FITR,TGA,MSCR,and temperature scanning tests,it was found that the most significant modification effect on asphalt mastic was achieved when the content of steel slag powder replacing limestone powder in SMBAM and SMSAM was 20% and 30%,respectively.Therefore,in the subsequent self-healing experimental design of this thesis,the effects of steel slag powder on the self-healing performance of asphalt mastic were studied,represented by 20% and 30% of steel slag powder replacing limestone powder in SMBAM and SMSAM.The self-healing properties of steel slag powder modified asphalt mastic under different healing environments were studied using linear amplitude scanning test(LASH),fluorescence microscopy test(FM),and molecular dynamics simulation(MS).The results showed that steel slag powder improved the self-healing performance of the matrix asphalt slurry,but decreased the self-healing performance of SBS modified asphalt slurry.Based on molecular dynamics simulation results,it is believed that the blending of steel slag powder with SBS modifier accelerates the movement of asphalt component molecules around the model,but limits the diffusion behavior of asphalt molecules towards the damaged interface,thereby constraining the healing performance of asphalt slurry.The recommended optimal healing temperatures for SMBAM(SSP0-LSP 100),SMBAM(SSP 20-LSP 80),SMSAM(SSP 0-LSP 100),and SMSAM(SSP30-LSP 70)are 50 ℃,40 ℃,60 ℃,and 40 ℃,respectively,and the optimal healing time is 20 minutes.