The Research Of Polyurethane Improve Performance Of CA Mortar Which Is Used For Plate-type Ballastless Track Of High Speed Railway

Slab ballastless track as the main track form of high-speed railway under the general trend of high-speed railway construction,its performance directly affects the safety and comfort of train operation on track.As an important part of slab ballastless track.CA mortar plays an important role in supporting,adjusting,reducing vibration,isolating vibration and resisting fracture lines for the whole ballastless track.However,cracks caused by freeze-thaw damage and low temperature vibration have appeared in the course of service.At present,there is a lack of systematic research on the deterioration of such damage at home and abroad.It is of great significance to improve the performance of CA mortar by adding modified materials and actively carry out research on CA mortar.In this paper,thermoplastic polyurethane elastomer is used as modified material to improve asphalt and CA mortar.It is divided into two different ways:one is to use polyurethane to modify asphalt,and then to prepare CA mortar;the other is to directly mix polyurethane with dry material to prepare CA mortar.The working properties of mortar,such as fluidity,air content,expansion,expansion rate,separation degree,flexural strength,compressive strength,Compressive-flexural ratio and elastic modulus,were studied.The results showed that the influence of polyurethane on the working performance of CA mortar improved with the increase of the content of polyurethane,and the mechanical properties increased first and then decreased with the increase of the content of polyurethane.The results show that the 5%content of polyurethane modified CA mortar improves the performance obviously,and the 0.8%content of polyurethane-CA mortar improves the performance better.The experimental group with better work and mechanical properties is selected for further study.In order to improve the cracks caused by freeze-thaw damage and low temperature vibration of CA mortar layer,the splitting strength,three-point bonding strength,four-point bonding strength and splitting bonding strength of CA mortar-concrete at 28 days old and after freeze-thaw,as well as the strength variation of specimens under chemical erosion and extreme temperature of 28 days old mortar were studied respectively.Finally,the freeze-thaw resistance,low temperature bending,dry shrinkage and creep property of CA mortar.The results show that the bonding strength,splitting strength,strength at extreme temperatures and bending properties at low temperatures of CA mortar and bonding interface are obviously improved by polyurethane,while the chemical erosion,dry shrinkage and creep property are slightly improved by polyurethane,and the performance of CA mortar modified by polyurethane is better than that of polyurethane-CA mortar.