Research On New Composite Modified Emulsified Asphalt And Its Micro-surfacing Performance

With the continuous improvement of the national road transportation network,the highway system has entered the stage of large-scale maintenance.As one of the effective means of pavement preventive maintenance,the micro-surfacing has the advantages of convenient construction and high economic benefits,and has been widely valued and widely used.However,shortcomings are gradually exposed at the micro-surfacing:On the one hand,the performance of the modified emulsified asphalt is not strong enough;on the other hand,micro-surfacing construction and road performance are insufficient.Problems such as segregation,grain loss and water instability during the service period remain to be resolved.In order to improve the performance of modified emulsified asphalt on the basis of meeting the requirements of the specification,SBR latex and C₉petroleum resin are selected as the composite materials of emulsified asphalt modifiers,and different emulsifiers are selected to study the emulsification of the asphalt.Firstly,the process and applicable conditions of various modified emulsification processes are studied and analyzed.And combined with the selected raw materials for preliminary experiments,the most suitable preparation process is determined as emulsification and modification.By adding two modifiers and different emulsifiers,the performance of the emulsified asphalt under various preparation conditions was compared and evaluated,and the optimal dosage of the two modifiers and the preferred emulsifier were obtained.And the optimum preparation scheme is obtained as follows:SBR latex content is 4%,C₉ petroleum resin content is 5%,emulsifier M content is 1.8%,the colloid mill emulsification operation takes 20 minutes.Lastly,SBR-C₉ modified emulsified asphalt has excellent performance.Aiming at the deficiency of construction and road performance when micro-surfacing is applied in road maintenance,the synthetic gradation A is designed based on the maximum density theory and gradation research,and the most widely used type MS-Ⅲmedium-value gradation（designated as gradation B）is used as the control group,and the mixtures of the two groups are compared under different oil-stone ratios.The test results shows that the performance of gradation group A mixture is excellent,with more outstanding mixing time,demulsification time,abrasion resistance and rutting resistance,however,its cohesion is not as good as the gradation group B mixture on the basis of meeting the requirements of the code,and there is still room for improvement.Through wet wheel abrasion test（WTAT）and load wheel adhesion test（LWT）,the best oil-stone ratio of gradation group A mixture is 6.9%.Finally,the best preparation scheme of micro-surfacing mixture is obtained:self-made composite modified emulsified asphalt and the designed optimized gradation group A are selected,the best oil-stone ratio is 6.9%,the amount of water added is 6%,and the amount of cement used is 1.5%.The performance of the emulsified asphalt mixture of the composite modified group and the single modified group is compared through the conventional road performance test and the water stability test.The test shows that the composite modified emulsified asphalt mixture has excellent comprehensive performance,its wear resistance,resistance to rutting deformation and water stability have obvious advantages.Through economic comparison,although the cost of the composite modification group will inevitably increase,but its performance is improved even more.Based on the high performance-price ratio,the composite modified emulsified asphalt and micro-surfacing is worthy of research and application.