Characterizing mechanical and multiscale porosity features of cementitious high sulfur tailings backfill using CT technology

Since cementitious high sulfur tailings backfill (CHSTB) produces acidification during mine filling, it severely affects the environment of underground mining and filling strength in a timely manner. Therefore, the current investigation analyzes the improvement effect of adding fly ash (FA) and sodium bicarbonate (SOB) to laboratory-made CHSTB specimens. Using some characterizing experiments like X-ray computed tomography CT, uniaxial compressive strength test, and SEM, alkali ratio effect on strength features, pore-fracture features and microstructures of CHSTB specimens was thoroughly emphasized. The experimental findings bared that adding SOB and FA additives to CHSTBs significantly improved their last compressive strengths, especially 1 % SOB, which had the most significant effect on microstructure. The CT slices and 3D reconstruction analyses disclosed that alkali addition could well lessen specimen’s porosity and promote formation of a complex fracture network. The resultant fissure morphology of specimens was strictly linked with the material’s strength property, revealing the influence of alkali agent on the damage mechanism of CHSTB specimens. Ultimately, this lab investigation offers an imperative foundation to further optimize CHSTB’s material proportions and to improve its final application in mining engineering in terms of cost-effectiveness, performance, and security.