Effect of initial defects on the microstructure, mechanics, and energy dissipation characteristics of cemented paste backfill

Numerous initial defects within the cemented paste backfill (CPB) adversely impair its physical characteristics; however, the mechanism for the effect of initial defects on the properties of the CPB is yet unknown. As a result, in this research, different contents of air-entraining agents (AEA) are incorporated into the CPB fabrication process to create varying degrees of initial defects inside the CPB. The CPB was then subjected to uniaxial compression, scanning electron microscopy (SEM), and nuclear magnetic resonance (NMR) testing to investigate the effect of initial defects on CPB mechanics, energy dissipation, and microstructure features. The findings of SEM and NMR studies demonstrate that the initial defects of the CPB are primarily microporosity and primary fractures. Incorporating the AEA increases the medium-sized and large-sized holes inside the CPB, reducing the density of the CPB's microstructure. The uniaxial compressive strength test results demonstrate that increasing the initial defects reduces the compressive strength and elastic modulus of the CPB and lengthens the compaction phase. Furthermore, when initial defects increase, the energy storage law before the peak of the CPB becomes more linear, and the energy dissipation law before the peak exhibits S curve features.

Automated summary

In this research, different contents of air-entraining agents were added during the fabrication process of cemented paste backfill to create various initial defects. The effects of these initial defects on CPB mechanics, energy dissipation, and microstructure were investigated using uniaxial compression, scanning electron microscopy, and nuclear magnetic resonance testing. The findings showed that the initial defects primarily consisted of microporosity and primary fractures, and the inclusion of air-entraining agents increased the presence of medium-sized and large-sized holes, reducing the microstructure density. Increasing initial defects resulted in decreased compressive strength and elastic modulus of the CPB and prolonged the compaction phase. Additionally, the energy storage and dissipation laws exhibited different patterns with the increase of initial defects.