Study on hydration reaction and structure evolution of cemented paste backfill in early-age based on resistivity and hydration heat

Abstract In order to reveal the hydration reaction of cemented paste backfill (CPB) more comprehensively, the non-contact electrical resistivity (NER) and microcalorimeter (TAM Air) were used to combine the hydration reaction with microstructure evolution of CPB in the early-age hydration process. The influence of tailings-cement ratio (TCR) on hydration reaction and microstructure evolution of CPB was studied, and the mathematical relationship model of resistivity and hydration heat of CPB was established; the kinetic parameters of CPB in the deceleration period were quantified by using the kinetic model; In combination with CPB’s unconfined compressive strength (UCS), the relationship between resistivity, hydration heat and UCS was established. The results show that the hydration process of resistivity and hydration heat characterization is highly consistent, which can be combined to characterize the hydration reaction and microstructure evolution of the CPB hydration process, and more comprehensively reveal the hydration reaction of CPB from a different perspective. Under different TCRs, the resistivity of CPB is affected by both tailings and cement. The content of tailings determines the overall value of its resistivity. As the content of tailings increases, the resistivity value increases, and the resistivity corresponds to the structural kinetic parameter K c increases; the hydration heat of CPB is mainly affected by the cement content. The higher the cement content, the higher the hydration heat, and the larger the corresponding hydration kinetic parameter K m . In addition, the hydration reaction process characterized by resistivity and hydration heat is dominated by cement content, the specific manifestation is that as the cement content decreases, the induction period will be prolonged, the acceleration period and the deceleration period will be shortened, and the reaction constants D and D ′ increase. The mathematical relation model of resistivity and accumulative heat release of CPB can realize the mutual characterization of resistivity and hydration heat.The resistivity and hydration heat of CPB under different TCR at 24, 36 and 48 h have good corresponding relationship with the UCS; the UCS of different TCRs at 28 days is negatively correlated with its resistivity at 48 h, and positively correlated with the hydration heat of 48 h. Studies have shown that the combination of resistivity and hydration heat can more fully reveal the hydration reaction and microstructure evolution of CPB, which is of great significance to the design of CPB.