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.

New Deposit of Mordenite–Clinoptilolite in the Eastern Region of Cuba: Uses as Pozzolans

“…Both the SiO 2 and the Al 2 O 3 (Table 2), are very important for the reaction of the mordenite-clinoptilolite with the Ca(OH) 2 in solution; in this sense, Rosell-Lam et al [11] reached a similar conclusion. This favours the fixation of free lime and the neutralisation of calcium hydroxide in solution, avoiding the later reaction with sulphates and chlorides [32]. The pozzolanic reactivity influences favourably the mechanical strength of the cement, mortars and concrete [33].…”

Chloride Penetration into Concrete under the Coupling Effects of Internal and External Relative Humidity

“…With rapid development of construction technology, concrete structure was inevitably exposed to various harsh environments, mainly including chloride attack, freezingthawing, and carbonation environments [1][2][3]. In particular, chloride penetration frequently resulted in the steel corrosion of reinforced concrete and reduced its service life, which was a key indicator for concrete durability [4,5]. Worldwide scholars have conducted a mass of studies to investigate the chloride penetration into concrete, and they found that the chloride penetration was different when concrete subjected to various exposure environments; moreover, the capillary absorption, concentration gradient, and convection provided the main driving force for chloride penetration into concrete [6][7][8].…”

Physicochemical Properties of Hydrated Portland Cement Blended with Rice Husk Ash

“…e durability of cement-based structures is a global pervasive problem. In view of changing environmental conditions due to climate change, there is a need to evaluate the performance of blended cements in aggressive media such as carbonation-prone environments [31,32]. e carbonationinduced corrosion is the major cause of degradation and subsequent reduction in the service life of cement-based materials and increased maintenance-related costs more so in structures located in coastal and offshore regions [33,34].…”