| The advantages of magnesium phosphate material contain high early strength,strong adhesion,good volume stability,etc.Used as a repair material of transportation infrastructure,magnesium phosphate material is conducive to the rapid resumption of traffic,strong bond strength with Portland cement and good volume stability.However,the setting time of magnesium phosphate material is short,which is unfavorable for site construction.The water resistance of magnesium phosphate material is poor and it will face severe challenges when suffering rains and snow.Meanwhile,the magnesium phosphate material is costly,which limits its application and development.In addition,as a vital repair material of transportation infrastructure,the research about the wear resistance of magnesium phosphate material is limited.In this paper,the setting time,strength,water resistance and wear resistance of magnesium phosphate material have been investigated.The physical effect of mineral admixture was discussed based on references of quartz powder and ultra-fine quartz powder.The chemical effect of mineral admixture was discussed by mixing mineral admixtures with KH2PO4.Moreover,the hydration mechanism and microstructure of magnesium phosphate material modified by mineral admixture were studied.Based on above-mentioned researches,the application of magnesium phosphate material modified by a large amount of admixture was explored.The main conclusions are as follows:（1）The reaction activity of modified magnesium phosphate material at early ages is decreased by the“dilution”effect of mineral admixture,while hydration degrees of Mg O and KH2PO4 at late ages are increased.（2）Chemical activities of copper slag powder,granulated blast furnace slag powder,ultra-fine metakaolin and ultra-fine limestone powder with KH2PO4 are strong,and the reaction products are hydrated ferrous phosphate,hydrated calcium phosphate,hydrated calcium phosphoaluminate,etc.The chemical activities of fly ash and fly ash microsphere with KH2PO4 are weak,and the reaction product is hydrated calcium phosphate.（3）Retarding effects of quartz powder and ultra-fine quartz powder are“dilution”effects while retarding effects of copper slag powder and ultra-fine metakaolin are mainly“dilution”effects.Retarding effects of granulated blast furnace slag powder and fly ash（microsphere）are strong.Granulated blast furnace slag powder reacts with KH2PO4 to produce Ca HPO4·2H2O at early ages,which consumes P ions and warps around Mg O particles to retard the dilution process of Mg O,while fly ash adsorbs Mg ions in pore solution.Compared with magnesium phosphate material added by retarder,magnesium phosphate material modified by mineral admixture has higher compressive strength at all ages under similar setting times.（4）With the cooperation of the“dilution”effect,“filling”effect,“chemical”effect and“hydrophobic film”,the water resistance of magnesium phosphate material modified by the hydrophobic agent with copper slag powder or with ultra-fine metakaolin is improved.（5）The wear resistance of magnesium phosphate mortar cloud be enhanced by adding 30%copper slag powder,granulated blast furnace slag powder,ultra-fine metakaolin or fly ash microsphere.The wear resistance of magnesium phosphate mortar has interrelationships with compressive strength,flexural strength and microhardness of hardened paste.（6）Considering particle shape,size and chemical activity,magnesium phosphate material modified by binary composite mineral admixture or ternary composite mineral admixture can obtain relatively high fluidity and long setting time,which meets the demand of site construction.Meanwhile,it achieves satisfactory strength at late ages. |
