Study On Micro Properties And Key Performance Of PMCM In Damage Repair Of Ballastless Track Structure

With the continuous growth of the service period of high-speed railway in China and the complexity of service conditions,a series of diseases have appeared in ballastless track,such as track slab cracking,missing corners,mortar layer defects and so on.Polymer modified cement-based composites(PMCM)are organic-inorganic composites with excellent properties,which can become an ideal repair material for ballastless track.In this paper,polymer,fiber and other additives are added into cement-based composites.A series of tests such as four-point bending and shrinkage tests are used to study its key properties such as strength,toughness,shrinkage and durability.The micro properties are studied by mercury intrusion instrument and scanning electron microscope.Finally,the mechanical properties of the composite specimens composed of cement-based composites and mortar matrix under complex conditions are also studied.The main conclusions of this paper are as follows:(1)The increase of fiber content can significantly improve the flexural strength and bending properties,which is mainly due to the bridging effect of fiber,which prevents the development of microcracks,and the bridging effect will be improved with the increase of fiber content;The increase of fly ash content can significantly improve the bending performance,but it will significantly reduce the strength.The increase of fly ash content will slow down the hydration process of cement paste,reduce the strength of base material,facilitate fiber pulling out and enhance the toughness of the material;When the content of polymer lotion and hydrophobic agent increases,the compressive strength decreases,while the flexural toughness first decreases and then increases,and the ultimate failure displacement decreases.(2)Increasing the content of fiber,fly ash and lotion can reduce the shrinkage of PMCM and improve the bond strength.After adding hydrophobic agent,the hydrophobicity will reduce the surface tension,reduce the shrinkage and significantly reduce the bond strength of PMCM.(3)Increasing the fiber content can significantly improve the acid salt corrosion resistance and frost resistance;The addition of fly ash can significantly improve the acid and salt resistance,but reduce the frost resistance;Increasing the content of polymer lotion will reduce the acid salt corrosion resistance,but will improve the frost resistance;Adding hydrophobic agent can improve its acid corrosion resistance and frost resistance,but it will reduce its salt corrosion resistance.(4)The addition of fiber will make the flexural failure mode of composite specimens change from type I brittle failure to type II ductile failure,the flexural strength will increase significantly,and the corrosion resistance coefficient will increase as a whole;With the increase of fly ash content,the flexural strength of composite specimens will gradually increase,the flexural failure mode is type II ductile failure,and the corrosion resistance coefficient also shows a downward trend;With the increase of lotion content,the flexural failure mode of composite specimens will change from type III interlayer debonding failure to type II overall failure,the flexural strength will also gradually increase,and the corrosion resistance coefficient will increase;The addition of hydrophobic agent will significantly reduce the flexural strength of the composite specimen,and the flexural failure will change from type II overall failure to type III interlayer debonding failure.The salt resistance will increase,but the acid resistance will decrease.There are 121 figures,25 tables and 82 references.