A Comparative Study On Early-stage Strength Development And Mechanical Properties Of Cement Emulsified Asphalt Mixture Using Different Fillers

With the development of highway construction in China,the use of hot mix asphalt materials is becoming more and more common,and the impact of hot mix asphalt on the environment is becoming more and more serious.The harmful substances and greenhouse gases generated by high temperature construction affect the environment in which we live.There are various measures to improve this phenomenon,and cement emulsified asphalt mixture is one of the methods to solve this problem.Cement emulsified asphalt mixture is a kind of semi-rigid pavement material formed by using cement instead of mineral powder in ordinary emulsified asphalt mixture after cold mixing,cold laying and rolling.The material has the advantages of cement concrete and asphalt mixture.However,cement emulsified asphalt mixture has a long health cycle and poor water resistance and fatigue performance.Studies have shown that the incorporation of different types of fillers will affect the hydration reaction of cement and the demulsification of asphalt in cement emulsified asphalt mixture to varying degrees,as well as its road performance.Therefore,this paper selects mineral powder,fly ash,hydrated lime and steel slag for research.In order to strengthen the environmental protection and recycling of waste resources,this paper also selected the brake pad waste,grinding to make it into a filler,and analysis together with the other four fillers.The strength formation of cement emulsified asphalt mixture mainly includes two processes of hydration reaction of cement and emulsion breaking of emulsified asphalt,and these two processes are related to the moisture in the mixture.In this paper,the effects of five kinds of fillers on the early strength of cement emulsified asphalt mixture were analyzed by XRD and SEM tests of cement emulsified asphalt mixture in different periods of moisture loss,splitting strength and strength formation.The results show that,with respect to the mineral powder mixture,in addition to the brake pad mixture,the other fillers reduce the moisture loss rate of the mixture and increase the splitting strength of the mixture.From the microscopic characterization of the mixture,the calcium hydroxide in the hydration product is concentrated on the surface of the aggregate,resulting in lower strength of the brake pad mixture,however,the brake pad packing not only improves the bonding ability of the asphalt but also fills the gaps,improves water damage resistance and fatigue performance.After the early strength analysis of the mixture,the road performance of the cement emulsified asphalt mixture was tested.The test results show that with the mineral powder mixture as the reference group,the other four kinds of fillers can improve the high temperature performance of the mixture;in terms of low temperature performance,fly ash mixture has good crack resistance,while other filler materials have a certain degree of decline;in terms of water stability,compared with the mineral powder mixture,the splitting strength ratio of the mixture of each filler is relatively small,among them,the brake pad mixture has the smallest decrease and the water stability is obviously improved;in terms of fatigue performance,the filler incorporation greatly improves the fatigue performance of the mixture;in terms of viscoelasticity,the main curve trends of various filler compounds are basically the same.However,compared with the hot mix asphalt mixture,the modulus in the high frequency(low temperature)environment is smaller than that of the hot mix asphalt mixture,and the modulus in the low frequency(high temperature)environment is larger than the hot mix asphalt mixture.It can be concluded that the cement emulsified asphalt mixture has better resistance to low temperature cracking and better rutting resistance than the hot mix asphalt mixture.The results of this study show that in the early strength,except for the brake pad filler,the other fillers have a certain improvement effect on the early strength formation of the cement emulsified asphalt mixture.In terms of road performance,the incorporation of fillers can improve the road performance of the mixture in addition to low temperature performance,and the improvement effect of the brake pad filler is obvious.