Research On Road Performance And Modification Mechanism Of Activated Coal Gangue Powder And SBS Composite Modified Asphalt Mortar

Coal is the main energy source of China that its annual production is almost near half of the world’s.Coal gangue produced during coal mining and washings it is one of the largest industrial waste in China.Its long-term open-air stacking creates environmental and personal security risks.Coal gangue has the dual attributes of waste and resources.The utilization rate of coal gangue resources in China is much lower than that in developed countries.In order to explore the feasibility of its application in high-grade asphalt pavement engineering,this paper studies activated gangue powder and SBS composite modified asphalt through road performance and modification mechanism.(1)Particle size analysis,specific surface area,scanning electron microscopy(SEM),pore structure and other experiments were carried out and found that activated Chenzhou(Hunan)coal gangue powder(ACG-A),activated Datong(Shan-xi)coal gangue powder(ACG-B),and activated Pingxiang(Jiangxi)coal gangue powder(ACG-C)have certain consistency in various physical properties.The mass loss of ACG-A is the largest,ACG-C is the second,ACG-B is the smallest.Among the three kinds of ACG,the mass loss is larger,the density is smaller,the specific surface area is larger,the pore structure is more developed,surface is rougher.Compared with Limestone mineral powder(LS),three kinds of ACG have smaller density,smaller particle size,larger specific surface area,more developed pore structure and rougher surface.X-ray difFraction XRD)results indicate that there are more active oxides and transition metal compounds in the activated gangue powder.The potential of activated gangue powder as a filler modifier is clarified by the technical characteristics of the filler.(2)Three kinds of ACG and LS were added into SBS modified asphalt by different flller-asphalt ratios(0,0.2,0.4,0.6,0.8,1.0,1.2)to be modified asphalt mortar.Cone penetration,softening point,force ductility,brookfield viscosity,repeated creep,and bending beam rheology(BBR)test were used to evaluate the road performance of each modified asphalt mortar.The results show that compared with LS mortar,the high temperature performance of each ACG mortar is improved and the ACG-A mortar is the most obvious,the low temperature performance is slightly reduced,and the temperature sensing performance is improved.Based on repeated creep and bending beam rheology(BBR),the double-line model was used to determine the optimum filler-asphalt ratio of ACG－A and LS as 0.92 and 0.99.(3)The modimication mechanism between ACG and asphalt includes surface wetting and interfacial adsorption.From the SEM,ACG is better wetted by asphalt.The adsorption of asphalt and ACG mainly includes physical adsorption,chemical adsorption and selective adsorption.The higher proportion of active oxides and transition metal compounds of ACG enhances the chemical adsorption strength to asphalt The developed pore growth improves the selective adsorption strength.The bridging effect of ACG makes the SBS network structure in the composite modified asphalt cement more stable so that ACG can improve the resistance to deformation of asphalt mortar.(4)During the mixture design,base on the optimal filler-asphalt ratio and maintain the oil－stone ratio,flne-tuning the gradation of asphalt mixture,determine the rationality of the gradation fine-tuning by comparing the performance of each mixture before and after fine-tuning.The ACG,LS+SBS modified asphalt mixture were tested by rutting test,bending test,immersion Marshall test and freeze-thaw split test to evaluate its high,low temperature and water stability.The results show that the composite modification of ACG and SBS improves the high temperature performance and water stability of the mixture,and the low temperature performance is slightly reduced.The correlation analysis shows the high and low temperature stability of the asphalt mixture has a good correlation with the high and low temperature properties of the corresponding mortar.The activated coal gangue powder and SBS composite modified asphalt are suitable for high.grade pavement in the hot and humid regions of southem China.