Mechanical Properties And Water Stability Of Bonding Between Fiber And Magnesium Phosphate Cement Matrix

Magnesium phosphate cement(MPC)has the characteristics of quick-setting and early-strengthening,hardening under negative temperature,strong bonding and low shrinkage,which are especially suitable for rapid construction and reinforcement engineering.But the brittleness is remarkable and the tensile resistance is weak,which limits the application of MPC.The addition of suitable fibers can strengthen and toughen the magnesium phosphate matrix.The effect of strengthening and toughening depends on the bonding properties between the fiber and matrix.In this paper,nano-particles and water glass were added to strengthen mechanical properties and water stability of bonding between fiber and MPC matrix.Firstly,the effects of nano-particles and water glass on the water stability of magnesium phosphate cement mortar were explored.Then,the effects of nano-particles and water glass on the bonding properties and the water stability of the bonding were investigated.In addition,the microstructure and phase analysis of matrix and the interface between fiber and matrix were carried out by XRD and SEM,revealing the influence mechanism of nano-particles and water glass on water stability.The main conclusions are as follows:(1)The incorporation of appropriate amount of nano-iron oxide(NF)improves the crystal integrity of magnesium phosphate cement mortar(MPCM)and enhances the stability and chemical bonding..With the increase of NF content,the compressive strength and water stability curve showed a trend of increasing first and then decreasing,and the optimum dosage was 2%.When the NF content is 1%~2%,the bond and its water stability are better.The hydration product such as dense iron phosphate formed by adding NF can inhibit the formation of interfacial cracks,and the effect of strengthening the water stability of bonding is remarkable.(2)The incroporation of an appropriate amount of nano-alumina(NA)fills the pores of the matrix,enhancing structural compactness.When the amount of nano-alumina is 6%,the strength before immersion is increased by 53.5%,and thestability of bonding water is increased by 7%.The addition of 6% NA has a significant improvement on the bonding and water stability,and the effect of improving the bonding properties is more significant.(3)Adding proper amount of water glass(WG)can improve the water stability of magnesium phosphate cement mortar(MPCM),and at the same time,the loss of compressive strength of the matrix is large because of agglomeration effect.The optimum dosage of WG is 1%.When the amount exceeds 1%,the compressive strength is greatly lowered.The incorporation of excess WG results in a significant decrease in adhension and water stability.(4)The fiber material properties and deformation treatment have the most significant influence on the bonding properties.The surface of straight steel fiber(SF)and end-hook steel fiber(HF)adhered the most matrix particles,followed by imitation steel fiber(ISF).Fine steel fiber(MSF)has more adhering particles only on the surface with damaged scratches.The bonding properties are ranked as follows:HF? ISF ? SF ? MSF.The bonding performance of HF is 1.5~2 times of SF.The material usage rate is as follows:ISF?HF?MSF?SF.And the surface of the fiber is roughened to improve the material usage rate of the fiber.