Compressive strength behaviour of sulphur tailings paste backfill: effects of binders and additives

Abstract

Aimed at the common later strength failure phenomenon in sulphur tailings cemented paste backfill (CPB), this paper studies loss ratio (Li) of the unconfined compressive strengths (UCS) of CPB, and analyses the effect of binders and additives on the UCS behaviour of CPB samples in the laboratory. In testing, when the sulphur content of tailings was 6.1% and the main sulphide was pyrite, the L120 of samples using ordinary Portland cement (OPC) as a binder was 47.4%. The sulphate-resistant cement (SRC) increased the UCS of samples for seven days by 84.2%, but the UCS for 14 and 28 days decreased by 13.3 and 43.1%, respectively. Portland composite cement (PCC) can obviously deteriorate the UCS of the samples. As the sodium silicate increased the samples’ UCS for seven days, the L28 was also raised. Comparatively, a proper amount of citric acid can reduce Li, and after seven days UCS did not decrease when the dosage was 0.5%. The L56 of samples with the binder mixed by OPC and slag was 14.6%, then the UCS increased gradually, and while continuing to add 0.5% citric acid the UCS had no loss. These findings demonstrate that changing binder and adding moderate additive can avoid the UCS loss of sulphur tailings CPB.