Coupled effect of curing temperature and age on compressive behavior, microstructure and ultrasonic properties of cemented tailings backfill

With the increase of mining depth in mines, the underground high-temperature becomes more and more serious. The main objective of this study is to investigate the coupled effect of curing temperature and age on compressive behavior, microstructural and ultrasonic properties of cemented tailings backfill (CTB). Unconfined compressive strength (UCS) testing was performed on the CTB specimens cured at 20, 35 and 50 °C for 3, 7 and 28 days, respectively. The X-ray diffraction (XRD), thermal analysis (TG/DTG), scanning electron microscope (SEM) and mercury intrusion porosimetry (MIP) were used to determine the microstructure and mineralogy of hardened CTB specimens. Furthermore, ultrasonic pulse velocity (UPV) testing was resorted to assess the relationship between UCS and UPV of CTB specimens. The results show that the compressive strength and microstructural properties of CTB are strongly affected by curing temperature and age. Higher curing temperature and longer curing time show significant enhancement effect on the compressive strength and refinement of pore structure of CTB specimens. The change in curing temperature leads to change in the mode of failure. The failure patterns of CTB specimens are mainly characterized by tensile, shear failure and hybrid failure. Furthermore, the relationship between UCS and UPV of CTB specimens was discussed and evaluated based on regression analysis. A linear relationship between UCS and UPV is obtained to assess the strength development of CTB as a nondestructive way.