Study On Preparation And Performance Of Cement Stabilized Macadam External Curing Agent In Desert Environment

In recent years,with the continuous development of highway construction in China,More and more projects are located in hot and dry desert areas.In the construction of road base in desert areas,the water evaporation is too fast because of high temperature,which lead to the insufficient strength and base cracking,seriously affecting the durability of the road.In order to ensure the pavement performance of the road base,it is often necessary to continue to sprinkle water for curing of the road base,which needs to consume a lot of valuable water resources in desert areas.This curing method not only causes the waste of human and material resources,which increases the cost of road construction,but also affects the normal construction progress.Therefore,if the curing methods such as sprinkling water can be replaced by curing agent for the road base,it will bring huge economic benefits to the project,and it is of great significance to save water resources and realize sustainable development.This paper screen out the appropriate film-forming components of curing agent.The film-forming effect and water retention properties of various single curing agents are studied,and the composite curing agent with excellent performance is prepared by orthogonal test.Then,the specimens of coating curing agent and uncoated curing agent are tested by simulating desert environment.The mechanical properties such as unconfined compressive strength,indirect tensile strength and durability of the specimens were studied,and the influence of curing agent on the road performance of cement stabilized macadam was analyzed.Finally,the hydration degree of cement was studied by means of SEM,TG and XRD to explore the curing mechanism of curing agent on cement stabilized macadam.The results showed that the composite of Paraffin emulsion,VAE emulsion,Alcohol ester-12 and Sodium silicate can effectively improve the water retention and mechanical properties of the specimens.Paraffin emulsion was used as the main component of film formation,and the optimum ratio of curing agent was determined by orthogonal test design:VAE content is20%,Alcohol Ester-12 content is 10%,Sodium silicate content is 18%.By simulating the desert environment,the road performance of cement stabilized macadam under different curing methods was compared,it was found that the compressive strength and splitting strength of the composite curing agent group（Paraffin-VAE-Sodium silicate group）were higher than those of the control group.The dry shrinkage resistance of cement stabilized macadam coated with composite curing agent is better,and the dry shrinkage coefficient is 116.26×10^-6 lower than that of cement stabilized macadam uncoated curing agent.The mechanical properties and durability of cement stabilized macadam mixture cured by curing agent meet the requirements of road performance in desert area.The hydration products（C-S-H gel,AFt and Ca（OH）₂）of curing agent group in desert environment were higher than those in blank group by XRD,TG and SEM test.In the curing agent group,the cement hydration degree of composite curing agent group is greater.