Bond performance of repair mortar made with magnesium phosphate cement and ferroaluminate cement

Abstract

This paper is aimed to investigate the bond performance of mortar with magnesium phosphate cement (MPC) as a novel-type repair material. This is achieved by mixing ferroaluminate cement (FAC) with MPC to prepare composite cement (MPC-FAC). Under standard and water curing conditions, the properties of MPC-FAC composite including setting time, ph, compressive and flexural bond strengths were tested. Experimental results show that adding FAC could significantly improve the compressive strength, flexural bond strength, water-resistance of FAC-MPC composite. Rough substrate interface contributes to the flexural bond strength of MPC-FAC mortar and OPC substrate. SEM-EDS was used to analyze the bond interface and micro-morphology of MPC-FAC before and after water immersion respectively. It was shown that the main reason for better bond performance is that the interface structure of MPC-40FAC composite and OPC substrate is more compacted, while MPC-40FAC composite microstructure is more integrated after water immersion. The three-zone model of the bond between OPC substrate and MPC-FAC repair material is also presented, which indicates that the interface bond behavior includes mechanical interlock, permeating and filling and secondary hydration. These promising results indicate that MPC-FAC composite can be used as a rapid-hardening repair material in the practical field.