Preparation And Properties Of Polyurethane Modified Cement Emulsified Asphalt

Cement emulsified asphalt mortar is widely used in railway construction,mainly composed of cement hydrates,emulsified asphalt,and sand,and plays a key role in supporting structures and track vibration reduction.In this article,waterborne polyurethane is used as a modifier,mainly studying the effects of different ionic types of polyurethane on the early slurry performance of cement emulsified asphalt,the influence of polyurethane content on the mechanical properties of cement emulsified asphalt,and the optimization of the mix ratio and preparation and curing process of polyurethane modified cement emulsified asphalt mortar.For the convenience of description,polyurethane is referred to as PU,cement emulsified asphalt is referred to as CA,and cement emulsified asphalt mortar is referred to as CA mortar.In Chapter 2,PU modified CA mortar was prepared and compared with styrene butadiene rubber(SBR)modified CA mortar and chloroprene rubber(CR)modified CA mortar.In Chapter 3,the influence of different ion types of PU on the early performance of CA slurry was mainly studied.The addition of anionic PU shortens the coagulation time of CA,while the addition of cationic PU prolongs the coagulation time of CA.From the rheological performance test results,it can be found that anionic PU can reduce the yield stress of CA,which is beneficial for free flow during construction.In Chapter 4,the influence of polyurethane content on the mechanical properties of cement emulsified asphalt was mainly studied.The dynamic mechanical analyzer was used to test the damping capacity and fatigue life of modified CA with different amounts of PU added.As the PU content increases,the damping capacity of CA increases,while the material stiffness first increases and then decreases.The fatigue life test results indicate that an appropriate amount of PU can extend the fatigue life of CA.Infrared spectroscopy analysis showed that the addition of PU to CA did not form new chemical groups.From the microstructure observed through SEM,it can be observed that due to the mutual adsorption of different ion particles,a core-shell structure covered by anionic PU is formed on the surface of cationic emulsified asphalt,and the asphalt is distributed in a spherical shape in the cement matrix.Chapter 5 mainly optimized the mix proportion and preparation and curing process of PU modified CA mortar.By adding additives such as water reducing agents and expansion agents,the expansion rate and air content of CA mortar were adjusted to meet the specifications.The optimal preparation process,curing temperature,and humidity of PU modified CA mortar were studied.This article first determined that the optimal polyurethane ion type for CA mortar modification is anionic,and then studied the effect of anionic PU content on the mechanical properties of CA.It was found that adding an appropriate amount of PU can improve the mechanical properties of CA in multiple aspects.The performance of CA mortar prepared by adding aggregates meets the requirements of relevant specifications,and has advantages over commonly used polymer modifiers.It has certain value for future high-speed railway construction.