To investigate the influence of cellulose ether on the fluidity and compressive strength of classified tailings cemented backfill (CTCB), hydroxypropyl methyl cellulose (in concentrations ranging from 0.1% to 0.3%) was utilized as a cellulose ether admixture. The variations in fluidity and strength of CTCB, both with and without cellulose ethers, were quantitatively assessed through rheological, expansion, bleeding, and unconfined compressive strength tests. Furthermore, the differences in microstructures of CTCB and the mechanism underlying cellulose ether-modified CTCB were investigated using chemical bonding water tests, scanning electron microscopy(SEM), and mercury intrusion porosimetry(MIP). The findings indicate that, compared to CTCB slurry without cellulose ether, at a concentration of 72%, an ash-to-sand ratio of 1∶4, and a cellulose ether content of 0.3%, the yield stress and plastic viscosity of the slurry increased by factors of 62.66 and 8.55, respectively, while the bleeding rate was completely eliminated.The addition of cellulose ethers to CTCB slurry results in increased yield stress and plastic viscosity, while simultaneously reducing the bleeding rate and enhancing the stability of the slurry.The effects become more pronounced with higher dosages of cellulose ethers. Notably, the expansion of the CTCB slurry decreases by 49.18%, indicating a negative correlation between cellulose ether dosage and slurry expansion, which suggests an adverse impact on the fluidity of the CTCB slurry.Furthermore, cellulose ethers exhibit an inhibitory effect on both the early (3 day) and long-term (28 day) compressive strength of CTCB. Specifically, when the cellulose ether content is increased from 0 to 0.3%, the 3-day compressive strength decreases by 49.44%, and the 28-day compressive strength decreases by 41.17%. The reduction in compressive strength becomes more significant with higher dosages of cellulose ethers. Scanning electron microscopy (SEM) analysis indicates that the incorporation of cellulose ethers does not alter the type of hydration products formed by the cementitious powders. The findings from the chemical binding water test suggest that incorporating cellulose ethers leads to a reduction in the content of hydration products. Observations utilizing mercury intrusion porosimetry (MIP) demonstrate that cellulose ethers introduce air, which subsequently increases the macropore content and overall porosity of the backfill. This results in suboptimal densification of CTCB. These research outcomes offer a valuable reference for the application of cellulose ethers in the modification of CTCB.
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