Application Reseach On Magnesium Phosphate Cement For Rapid Repair Of Ballastless Track

Magnesium phosphate cements(MPCs),kinds of novel cementious materials,based on through-solution acid-base reaction,are characteristics of fast setting,high early strength,high bonding strength and good volume stability.According to the complex conditions of operation and loading,ballastless track maintenance requires patching materials to be controllable in setting time and durable.However,current patching materials can hardly meet the requirements.It is of great benefits to apply MPCs in ballastless track maintenance,which would widen the applications of MPCs as well as promote the technology of ballastless track maintenance.In light of the requirements of ballastless track maintenance,the following performances of magnesium phosphate cements were studied:(1)Based on the operation time of ballastless track,this paper studied setting time of MPCs;secondly,according to the outdoor environment of ballastless track,water stability was investigated.The effects of alumina on water stability of MPCs had also been studied.Results showed that phosphates significantly influenced the setting time and temperature evolution during curing reaction.The setting time of MPCs could be controlled from 5 to 20 min through the adjustment of phosphates content.Alumina could improve water stability,refined the porosity and increased the mechanical strength of MPCs.MPCs has good bonding strength,small shrinkage and large fluidity to meet the requirements of ballastless track maintenance.(2)Based on ABAQUS software,the ballastless track finite element model was modeled.Finite element model of ballastless track with preinstall crack had also been established for studying the effects ofpatching materials MPCs and epoxy resin on the ballastless track model under load.Finite element simulations results showed that magnesium phosphate cement could decrease the maximal stress of ballastless track slab and work collaboratively with old concrete.When cracks in ballastless track slab are wider than 3mm,MPCs exhibits better performance in ballastless track maintenance than epoxy resin.