Bond behavior between the nano-Al2O3-water-glass-modified magnesium-phosphate-cement mortar and steel fiber

Abstract In recent years, the magnesium phosphate cement (MPC)-based polymer is a potential type of material to quickly repair existing structures due to some distinguished advantages. In this paper, a series of experimental studies were conducted to evaluate the effects of the nano-Al2O3 (NA) substitution rate, water glass (WG) substitution rate and immersion time on the bond behavior between the magnesium phosphate cement mortar (MPCM) and steel fiber (SF). The main properties of the pull-out specimens were examined, including the bond strength, energy consumption of steel fiber pull-out, and water stability of the MPCM-SF interface evaluated by the bond strength retention rate and relative bond strength retention rate. In addition, the micro analysis of the fiber-matrix interface transition zone (ITZ) were conducted by using the Scanning Electron Microscope (SEM), and the compositions analysis of the MPC paste with NA and WG were conducted by using X-Ray Diffraction (XRD). The experimental results indicated that regardless of the immersion time, the NA substitution rate of 4% and 6% had a clearer improvement on the bond behavior between MPCM and SF than those of other types of the specimens; the WG substitution rate of 1% and 2% had a more significant improvement on the bond behavior between MPCM and SF than those of other types of the specimens; the distance between the larger width crack and the steel fiber for the specimen with a NA substitution rate of 6% was larger than than those of other types of the specimens, which showed that the ITZ between MPCM and SF with NA substitution rate of 6% exhibited a denser micro-structure and better micro-mechanical properties; the micro-structure of the ITZ between MPCM and SF gradually deteriorated as the immersion time increased, which showed that the water stability of the MPCM-SF interface gradually decreased.