Effect of Steel Fiber on Mechanical Properties and Microstructure of Magnesium Phosphate Cement–Based Concrete Exposed to Water and Sulfate Attack

Abstract

Recently, steel fiber–reinforced magnesium phosphate cement–based concrete (SFRMPCC) has attracted much attention due to its excellent properties. To apply this new type of concrete to practical engineering, this paper evaluates the effect of steel fiber (SF) content and curing age on the water and sulfate resistance of magnesium phosphate cement–based concrete (MPCC). Specimens containing fly ash and metakaolin and with different SF volume contents were prepared and subjected to curing in air, water, and 5% Na2SO4 solution. The mass change, cubic compressive strength (CCS), strength retention rate, deterioration factor, microstructure, and phase composition were analyzed. Empirical formulas for strength prediction are proposed using range, variance, and nonlinear regression analysis methods. The results showed that the specimens immersed in water and Na2SO4 solution had good mass retention. The compressive strength of air-cured specimens gradually increased with the curing age, and the addition of a proper amount of SF could improve the strength under air curing. However, the addition of SF had a negative effect on the compactness and strength of specimens immersed in water and sulfate solution. SFRMPCC and MPCC had good resistance to sulfate attack, which may be related to the new reaction in the magnesium phosphate cement (MPC) matrix.