Hydration mechanism and mechanical-thermal correlation of cemented paste backfill under different curing temperatures

Abstract

The external ambient temperature plays a crucial role in influencing the hydration process of cemented paste backfill (CPB), causing notable variations in overall structure and physical-mechanical properties. To precisely analyze mechanical properties under different curing temperatures, a uniaxial compression strength (UCS) experiment was conducted. A real-time data acquisition system was established to monitor temperature, volumetric water content, and resistivity. Hydration heat measurement and low-field nuclear magnetic resonance (NMR) experiments were performed to analyze the hydration mechanism and the correlation between mechanical properties and thermal effects during the consolidation period. The study revealed that the relationship between UCS, elastic modulus, and curing temperature can be quantitatively characterized using polynomial functions. The mechanical parameters reach their peak values at a curing temperature of 40 °C. However, exceeding 40 °C leads to excessively rapid hydration rates, causing a decrease in hydration degree, and extremely high hydration rates result in reduced microstructure compactness. Under different curing temperature conditions, CPB exhibits substantial temperature effects in terms of volumetric water content, electrical resistivity, hydration heat, and NMR data, effectively characterizing the hydration mechanism. The hydration reaction unfolds through stages: initial induction, accelerated development, decelerated development, stable development, and hardening formation. As the curing temperature rises, the completion times of each stage exhibit a significant exponentially decreasing trend. Moreover, the application of the GA-BP neural network algorithm has unveiled inherent patterns between the monitoring results of CPB's hydration process and its macroscopic strength. Computed results show that the relative errors in predicting strength at various curing temperatures are all less than 0.1 %.