Effect of silica fume and basalt fiber on the mechanical properties and microstructure of magnesium phosphate cement (MPC) mortar

Abstract

This paper evaluates the effect of silica fume (SF) and basalt fibers (BF) on the mechanical properties and microstructure of magnesium phosphate cement (MPC) mortar. Several MPC mortar mixtures with different contents of SF and BF were prepared. Experimental results revealed that the compressive strength and flexural strength of MPC mortar was increased by increasing the percentages of SF from 0% to 10%. Incorporation of BF improved the flexural strength and post-peak flexural behaviour of the load-deflection curve of MPC mortars, but its effect on the compressive strength was insignificant. MPC matrix with 10%SF and 0.5%BF demonstrated the highest compressive and flexural strength of 49.42 MPa and 5.31 MPa respectively at the 28 days. XRD and SEM analysis showed that control mixture without SF and BF contained more unreacted magnesia and struvite as compared to MPC mortars containing SF and BF. Moreover, SEM-EDS analysis of MPC mixtures incorporating SF and BF showed that SF and fly ash (FA) reacted within the MPC paste system to produce the secondary hydration products. It was postulated that magnesium silicate, aluminium or silicon phosphate phases were formed during the reaction of SF and FA in the MPC system. These secondary products tend to improve the bonding of solid phase and hence mechanical properties of MPC mortar. Finally, SEM-EDS analysis also confirmed the excellent interaction of BF with the MPC hydration products.