Compressive strength development and microstructure of magnesium phosphate cement concrete

Abstract

In order to verify the feasibility of preparing structural concrete with magnesium phosphate cement (MPC), the workability, temperature rise and compressive strength of MPC concrete were studied. The hydration products, pore structure and fractural morphology of MPC concrete were also investigated. The results show that the hardened MPC stone is a ceramic-like structure by cementation of unreacted magnesium oxide and fly ash with the solid solution of the hydration products of fly ash and struvite. The continuity of this kind of ceramic-like structure will be broken when the aggregate is added to prepare concrete, and a weak interface transition zone will be formed between the ceramic-like structure and aggregate due to the “wall” effect, but the 2-hour compressive strength can still reach more than 40 MPa. The heterogeneous structure of MPC concrete results in a power function decreasing of concrete compressive strength in later stage with the increase of specimen sizes.