Toughness and strength of PVA-fibre reinforced magnesium phosphate cement (FRMPC) within 24 h

Cement with high toughness and early strength are widely utilized in the field of rapid repair. This study is focused on the development of PVA fibre reinforced magnesium phosphate cement (FRMPC) that possesses these properties. The compressive, flexural, and tensile strengths of the FRMPC were measured at various ages, including 1, 2, 3, 4, 5, 6 and 24 h. The relationships of the element contents, hydration products, hydration process, and the microscopic morphology with the mechanical properties were analyzed. Importantly, the mechanical formation process of the 6 h was analyzed in detail. Results show that the tensile strain of the FRMPC exceeded 3% at all ages, and the flexural strength was greater than 10 MPa at all ages. The compressive strength reached 15.53 and 25.63 and 32.48 MPa after 1 h, 6 h and 24 h, respectively. The ultimate tensile strength, flexural strength and compressive strength of 6 h reached 98%, 90% and 78% of the final strength of 24 h.The incorporation of fly ash and quartz sand mitigates the exothermic rate of hydration and optimizes the filler structure. Furthermore, the addition of fly ash engenders an amorphous phase gelling material and MgSiO3, characterized by effective filler properties.This results in an enhanced integration of PVA fibres with the cement matrix, thereby exhibiting improved toughness.The main hydration product was MgKPO4 × 6 H2O, and its formation rate and amount affected the mechanical properties. The nature of the hydration products and the density of the specimen structure were determined to be key factors in the progression of uniaxial tensile properties. FRMPC's strength, toughness and shrinkage are in a relatively good state, and the potential for its early-stage mechanical properties still can be improved.