Effect of temperature variation on bonding properties of magnesium potassium phosphate cement: A multiscale analysis

In magnesium potassium phosphate cement (MKPC) repair work, varying ambient temperatures significantly affect the repair outcomes. To quantitatively characterize the effect of temperature variation on the bonding properties of MKPC, this paper comprehensively explores the issue at multiple levels, evaluating the bonding properties of the combined specimens using double-shear tests, scanning electron microscope tests, and nuclear magnetic resonance tests, followed by quantitatively characterizing the form of interfacial damage using digital image processing of interfaces. Finally, the Pearson correlation coefficient method was employed to analyze the correlation between different scales. The results indicate that, for the MKPC combined specimens, the interface shear bearing capacity slightly decreased at low temperatures and improved back to normal temperature, with a retention coefficient (K) of 0.977. The internal structure was dominated by small holes, whereas at high temperatures, the capacity severely decreased, with K only 0.4, and a large number of large holes and cracks were present internally. The DIP results reveal that the interface damage forms of the combined specimens at low temperatures were dominated by the MKPC-NC interface, which accounted for 76.38 %. At high temperatures, the damage was mostly within the MKPC, with the MKPC interface accounting for 52.06 % of the fracture interface of the specimen. Pearson correlation analysis demonstrates that temperature has a strong relationship with the scale indicators, with an |R| value greater than 0.7. The |R| value between macroscopic performance and microstructure is 0.95, providing strong evidence that macroscopic performance can be characterized by the microstructure.