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

• Published in: Construction & building materials 2021-04, Vol.279, p.122398, Article 122398
• Main Authors: Jia, Liang, Zhao, Fangli, Yao, Kai, Du, Hongjian
• Format: Article
• Language: English
• Subjects: Bond interface; Flexural bond strength; Magnesium phosphate cement; Water resistance
• ISSN: 0950-0618; 1879-0526
• DOI: 10.1016/j.conbuildmat.2021.122398

•Influences of the FAC content and curing conditions on the bond performance of MPC-FAC composite were studied.•The chemical composition and microstructure of the fracture interface were analyzed.•Enhancement mechanism between MPC-FAC mortar and OPC substrate was characterized. 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.