Chapter 4 - Cementing sulfur tailings using low-clinker cement

Abstract

Sulfidic tailings (STs) with excessive sulfur content are vulnerable to oxidation, which generates sulfates, leading to incompatibility with cement clinker. In this regard, M32.5 cement was used as the binding material in low-clinker cement to mitigate this incompatibility. The effect of the STs on the properties of the M32.5 cement mortar was studied in this work. An experimental study was conducted to evaluate the effects of different substitution percentages (0%, 10%, 20%, 30%, 40%) on the compressive strength, fluidity, and expansion ratio of the M32.5 cement mortar. The addition of STs reduced the fluidity of the mortar, and it decreased with the increase of STs dosage. The compressive strength of the mortars increased at lower substitution rates (0%–20%) but decreased at higher substitution rates (>20%). Ettringite peaks and new sulfate peaks were found by X-ray diffraction. Scanning electron microscope observation of the microstructure showed that many hydrated products, such as ettringite, were formed and filled in the interstitial spaces, which encouraged strength development. The optimal replacement ratio of STs for river sand was 10%.