Research On Strength Mechanism,Improvement Method And Road Performance Of Cement Emulsified Asphalt Mixture

As a cold mix asphalt mixture,cement emulsified asphalt mixture is widely used at home and abroad to solve the problems of energy consumption and greenhouse gas emission caused by hot mix asphalt pavement.Compared with the traditional hot mix asphalt mixture,the cement emulsified asphalt mixture has the problems of lower strength,higher porosity,serious water damage,poor durability and the like.Understanding the strength formation mechanism of cement emulsified asphalt mixture,improving the strength of cement emulsified asphalt mixture and improving the adhesion between emulsified asphalt and aggregate are the keys to solve the above problems.Aiming at the strength formation mechanism of cement emulsified asphalt mixture,this paper carried out research on the influence mechanism of cement dosage and water addition amount on the strength and void ratio of cement emulsified asphalt mixture,studied the improvement method of cement emulsified asphalt mixture performance,and analyzed and evaluated its road performance.Through the study of splitting tensile strength and void ratio of emulsified asphalt mixture with different cement dosage and different water content,the rheological characteristics of mixture cement,residual water content of specimen and scanning electron microscope pictures were analyzed comprehensively.The results show that the void fraction of the mixture decreases first and then increases with the increase of water content.The change of cement dosage has no obvious influence on the void ratio of the mixture.The splitting strength of the mixture increases first and then decreases with the increase of water content.When there is more water added,the mixture will be more dense when it is formed,and the cement has better penetration and wrapping ability on aggregate.But it will lead to more pores inside the cement and loose cement structure.The increase of cement dosage can reduce the pores in the cement paste of the mixture and improve the compactness of the cement paste.The residual evaporable water in the mixture sample is reduced,and the influence of water on the cement strength is reduced.When the amount of water added is small,the cement dosage will increase,which will reduce the fluidity of cement paste and reduce the wrapping effect of cement paste on aggregate.In order to improve the mechanical properties of the cement emulsified asphalt mixture and reduce the void ratio of the mixture,improvement research was carried out by using water reducing agent,using high permeability emulsified asphalt,improving the mixing method of the mixture,and changing the forming method of the mixture.The research shows that the use of water reducing agent can improve the strength of cement emulsified asphalt mixture and reduce the void ratio of the mixture.When the amount of water added is small,the use of high permeability emulsified asphalt can improve the splitting tensile strength of the mixture and reduce the void fraction of the mixture.The mixing method of cement emulsified asphalt mixture is recommended: firstly,coarse aggregate,fine aggregate,mineral powder and cement are evenly mixed;Then adding external water for stirring so that coarse and fine aggregates,mineral powder and cement are fully contacted with the external water to form a water film on the surface;Finally,emulsified asphalt is added for mixing.When the amount of water added to the mixture is relatively low,it is recommended that the cement emulsified asphalt mixture test piece be formed by one-shot compaction(75 times of compaction on both sides of the test piece).Based on the emulsified asphalt mixture with improved measures,the road performance of the improved cement emulsified asphalt mixture was studied and the hot mixed asphalt mixture was compared and analyzed.The research shows that the improved cement emulsified asphalt mixture meets the requirements of the code for water stability and high temperature stability of hot mix asphalt mixture,and has strong anti-rutting ability.Although the modified emulsified asphalt cement has improved the wrapping property of aggregate,its anti-stripping ability is still low.The above research has clarified the influence mechanism of cement dosage and water addition on the strength of cement emulsified asphalt mixture.The problems of low strength of cement emulsified asphalt mixture and poor adhesive force of cement paste are preliminarily solved.The improved cement emulsified asphalt mixture has the feasibility of being applied to the middle layer or the lower layer of the high-grade pavement.However,its anti-stripping ability is relatively low and its performance needs to be further improved.