Effect of Sulphate and Chloride Ingress on Selected Cements Mortar Prisms Immersed in Seawater and Leather Industry Effluent

Abstract

Cement structures are major capital investments globally. However, exposure of cement-based materials to aggressive media such as chloride- and sulphate-laden environments such as coastal areas affects their performance. Ordinary Portland cement (OPC) is the main cement used in buildings and civil structures such as dams and bridges. This paper reports the findings of an experimental investigation on the effect of ingress of Cl− and SO42− on compressive strength development and the ions’ diffusivity in selected OPC brands in Kenya. The aggressive media used included seawater (SW) and wastewater from leather industry (WLI). Three brands of commonly used cements of OPC in Kenya were used. Mortar prisms were prepared from each brand of cement at different water-to-cement ratios (w/c) of 0.5, 0.6, 0.65, and 0.7 and allowed to cure for 28 days in a highly humid environment. The aggressive ions’ ingress in the mortar prisms was accelerated using a potential difference of 12 V ± 0.1 V. Analysis of diffusivity and diffusion coefficient of Cl− and SO42− was finally done. Compressive strength analysis was done before (at the 2nd, 7th, 14th, and 28th day) and after exposure to the aggressive ions. The results showed that the diffusivity of chlorides was more pronounced than that of sulphates. Diffusivity was observed to be higher at higher w/c ratios for all cement categories. It was observed that compressive strength increased with curing age, with the highest observed at 28 days. Cement A was generally found to have the highest compressive strength for all w/c ratios. The compressive strength was observed to increase after the mortar prisms were exposed to SW as opposed to the ones exposed to WLI. Generally, it was also observed that the strength gain increased with increase in w/c. The loss in strength was also observed to increase with increase in w/c.