Study on mechanical properties and mesoscopic damage mechanism of metakaolin modified recycled aggregate concrete

This research explored the effect of water-binder ratio (w/b) and curing age on the mechanical properties, microstructure, and damage mechanism of modified recycled aggregate concrete (RAC) with metakaolin (MK). The consequence appeared that the mechanical properties of the specimens were positively correlated with curing age, but negatively correlated with w/b. In addition, the incorporation of MK increased the peak stress, elastic modulus and peak strain of the specimens with w/b of 0.65 by an average of 17.46% and 8.42% at six ages. Through microscopic test, it was found that the mechanical properties of the specimen were related to the hydration reaction, and the continuously generated gel products made the matrix structure more compact. Based on the statistical damage theory, the influence of w/b, age and MK on the damage evolution of mesoscopic fracture and yield were quantitatively analyzed, and a correlation between macroscopic mechanical properties and the mesoscopic damage mechanism was established.