Slurry Design And Properties Experimental Study Of High Fluidity Potassium Magnesium Phosphate Cement

Potassium magnesium phosphate cement?MKPC?is a new inorganic cementitious material composed of magnesium oxide,soluble phosphate and retarder.There is still much room for development.If MKPC slurry has high fluidity,it can be used in anticorrosion coating or embedded material with high pressure spraying and grouting technology.It has a wide application prospect in the market.In this paper,author studied on MKPC slurry with large fluidity.In the prophase,a large number of exploratory experiments were done in order to determinate the basic mix ratio of MKPC slurry with large fluidity.The parameters such as fluidity,strength change,volume deformation,hydration temperature,volume stability and water absorption were used as characterization parameters,and through three micro-testing methods of XRD,TG/DTA and SEM,the effect of chemical additive water glass on the MKPC slurry mixed with compound retarder at high water/adhesive ratio was studied.It is found that water glass can greatly improve the early strength of the specimen and solve the contradiction between large fluidity and early strength.The alkaline water glass solution can also delay the hydration reaction and further increase the fluidity of the slurry so that the slurry is in a self-leveling state.In addition,water glass can also block pores after slurry hardening,and it can also react with Mg²⁺in the system to further dense pore size of magnesium silicate hydrate gel,reduce evaporation of capillary water,and improve the volume stability and water stability of hardened body.But the later strength development is not as good as that of the blank group.On this basis,we continue to add silica fume,metakaolin and fly ash to study the effect of mineral admixture on the high fluidity MKPC slurry.By adding mineral admixture can modify and optimize the hardenite and prepare the MKPC paste with better performance.It is found that the compressive strength of hardened body can be significantly increased with the addition of metakaolin,and the adhesion between MKPC paste and ordinary Portland cement mortar can be improved by adding fly ash.Then the research object is extended to MKPC mortar.The effect of aggregate and mineral admixture on the performance of large fluidity MKPC mortar is studied.It is found that the use of quartz sand has higher mechanical properties and better volume stability than river sand when the cement sand ratio is at a certain time.When using the same aggregate,the strength is higher with larger cement sand ratio.The micro aggregate action and volcanic ash action of mineral admixture can also greatly improve the properties of MKPC mortar.The heterogeneous nucleation action of mineral admixture particles can significantly increase the early strength of hardened body.The secondary hydration reaction between the active component and phosphate also greatly increased the late strength.The improvement of volume stability of mineral admixture also reduces the micro-stress of bonding interface with ordinary Portland cement mortar then increases the bond flexural strength.Mineral admixtures with smaller average particle size make the hardened body more compact and thus improve the water stability of the specimen.Based on the test of material properties,the application of high fluidity MKPC slurry was explored.It is found that the three dimensional spacer fabric can significantly improve the impact resistance and deformation ability of the composite.Therefore,it is proposed to be used as a joint material for assembled concrete wall panels.As a waterproof coating material to increase the impermeability of ordinary concrete,because the material itself is a dense ceramic-like structure,the thickness of 2.5mm coating can reach the highest standard of the national standard of concrete quality.The anti-seepage effect of MKPC is remarkable,and the application prospect is wide.