Pore and strength characteristics of cemented paste backfill using sulphide tailings: Effect of sulphur content

Abstract

Cemented paste backfill (CPB) is a special composite prepared from recycled tailings, cement, and water. To ensure safe and efficient application of CPB for sulphide tailings, its pore and strength characteristics should be investigated. Although the strength of CPB has been determined well, identification of pore characteristics often requires manually adjusted threshold during the pre-treatment of microscopic images. In this study, an annealed chaotic competitive neural network was used for the pre-treatment of microscopic images and analysis of particles (pores) and cracks for quantitative pore analysis. The effect of sulphur content on the pore and strength characteristics of CPB specimens was evaluated in this study. Microscopic parameters (porosity, fractal dimension, etc.) were used to represent the pore characteristics, and unconfined compressive strength (UCS) was used to represent the CPB strength. The results show that the sulphur content plays a critical role in the pore and strength characteristics of CPB. For example, the porosity first decreased from 9.5% to 8.2% and then increased from 8.2% to 12.89% when the sulphur content was increased from 6.1% to 25%. Instead, the UCS of CPB specimens showed a slight increase from 2.51 MPa to 2.90 MPa before a clear decrease from 2.90 MPa to 0.571 MPa. The results indicate that it is necessary to evaluate the effect of sulphur content before the sulphide mineral tailings are recycled in CPB.