Experimental study on mechanical properties and fracture toughness of magnesium phosphate cement

• Different types of strength of MPC with or without fly ash were studied.
• The effects of fly ash on various types of strength were compared and analyzed.
• Relationship among axial tensile, splitting and compressive strength was analyzed.
• The fracture characteristics of different MPC were studied.

The mechanical properties and fracture toughness of magnesium phosphate cement (MPC) were studied in this paper. The results show that the strengths (compressive, flexural, axial tensile and splitting strengths) of MPC increased rapidly over curing ages and then increasing rates slowed down. The compressive strength increased with the addition of fly ash, while the tensile strength decreased. For both the specimens with and without the addition of fly ash, the axial tensile strength was lower than the splitting strength. The axial tensile strength of MPC without fly ash was 1/13–1/10 of compressive strength and the axial tensile strength of MPC with fly ash is 1/17–1/14 of compressive strength. The ratio decreased over time. The load–deflection curve showed the failure mode of MPC is brittle failure. The fracture energy increased over time, while the value was relatively small. The failure load and the corresponding mid-span deflection of MPC decreased in presence of fly ash, which results in the further decrease of fracture energy of MPC.