Early-age Mechanical Properties And Engineering Performance Of Cement Emulsified Asphalt Mixture With Combined Usage Of Cement

At present,road engineering in my country has shifted from the construction stage to the maintenance stage.As the most important pavement form of the current expressway,the common diseases of asphalt concrete pavement include:looseness,potholes,rutting,rolling,waves,and congestion.Diseases not only reduce the comfort during driving,but also greatly endanger driving safety.Coupled with the coupling effect of the natural environment,it is easy to cause early damage to the road base and subgrade.Hohhot is located in the central part of my country’s Inner Mongolia Autonomous Region.It has a typical Mongolian plateau continental climate.The climate changes in four seasons,with large annual temperature differences and large daily temperature differences.Severe weather conditions put high demands on the maintenance of asphalt pavement.Based on this,it is urgent to develop a repair material with early strength and excellent road performance to meet the requirements of repair engineering.This study developed a new type of cement emulsified asphalt quick repair material by adjusting the mixing amount of ordinary Portland cement and sulfoaluminate cement,the combination method and the ratio of emulsified asphalt.The performance of the new cement emulsified asphalt was studied.The results show that the work performance of the repair material decreases with the increase of cement consumption,especially when the cement consumption is 6%,the slump and working time of the repair material are significantly reduced compared with the repair material with 2%cement consumption.Therefore,in order to ensure the excellent construction performance of the repair material,it is recommended that the amount of cement does not exceed 4%.The combined use of silicate and sulphoaluminate cement has little effect on the working performance of the mixture.The early mechanical properties of the new cement emulsified asphalt were studied.The results show that the early mechanical properties of the repair material increase with the increase of cement content.When the cement content is 4%,the compressive strength of the repair material increases by more than 60%,and the flexural and tensile strength increases by about 15%.When the ratio of Portland cement to sulfoaluminate cement is 90:10,the effect of improving mechanical properties is the best.The bonding strength between the repair material and the cement concrete is slightly higher than that of the asphalt mixture,indicating that the repair material may be better than the asphalt mixture in repairing the cement concrete pavement.The early water stability,frost resistance,wear resistance,high temperature stability and low temperature crack resistance of the new cement emulsified asphalt were studied.The results show that for improving the water stability and abrasion resistance of the repair material,the optimal amount of cement is recommended to be about 4%.When the mass ratio of silicate and sulphoaluminate cement is 90:10,the loss of the repair material is only 9.8%;and after 200 freeze-thaw cycles,the mass loss rate of the repair material is less than 5%.The increase of cement dosage is positively correlated with high temperature stability,and negatively correlated with low temperature crack resistance.Compounding cement can improve the low temperature crack resistance of repair materials to a certain extent.The 4 h compressive strength of the repair material has a good correlation with the long-term road performance,and the correlation coefficient(R~2)both exceeds 0.88.Characterize its microstructure characteristics by SEM and XRD techniques.The results show that as the amount of cement increases,more ettringite,calcium hydroxide and C-S-H gel can be generated,which is beneficial to the formation of CAM sample strength.The combined use of Portland cement and sulphoaluminate cement further improves the microstructure compactness of the repair material and the number of hydration products,and at the same time optimizes the pore structure of the repair material.The addition of cement increases the demulsification process of emulsified asphalt.