Non-isothermal evolution of mechanical properties, pore structure and self-desiccation of cemented paste backfill

Abstract

In the field, cemented paste backfill (CPB) structures are subjected to non-isothermal curing conditions. In this study, the non-isothermal strength, pore structure development, and self-desiccation of CPB were investigated. CPB specimens with different types of binders and tailings were prepared and cured under isothermal (room temperature: 20 °C) and field non-isothermal conditions. Unconfined compressive strength (UCS) tests, microstructural tests and analyses as well as monitoring experiments, were conducted on CPB specimens cured over various ages. The obtained results show that the non-isothermal curing condition significantly increases the strength as well as the strength increase rate of the CPB regardless of the type of binder and tailings used. Moreover, the non-isothermal condition leads to more intense self-desiccation of CPB as well as the refinement of the pore structure of CPB due to the generation of more hydration products, such as calcium–silicate–hydrate (C–S–H), in the non-isothermal CPB. It is also found that a mine cavity (stope) backfilled with CPB material made with Portland cement type I (PCI) has a significant advantage over stope backfilled with CPB made with slag/PCI (50%/50%) in terms of strength formation and enhancement of self-desiccation due the difference in the non-isothermal curing conditions. The findings of this study provide insight into the development of the mechanical and microstructure properties as well as self-desiccation of CPB structures when exposed to field thermal curing condtions, thereby contributing to the improvement of mechanical stability and economic performance of future CPB designs. The impact of non-isothermal curing conditions on CPB properties need to be considered in mine backfill design and operations.