Abstract
This research studies the properties of mortars incorporating waste materials including red mud (RM), ground granulated blast furnace slag (GGBFS), and electric arc furnace dust (EAFD). Ordinary Portland cement (OPC) was partially replaced with equal contents of RM, GGBFS, and EAFD at different ratios by weight (0, 5, 10, 15, 20, 30, 40, and 50%). Slump, compressive strength, splitting tensile strength, electrical resistivity, water absorption, resistance to freeze–thaw cycles, and durability under sodium sulphate and sulphuric acid attacks were investigated. Moreover, the microstructure of mortars cured in tap water and exposed to sulphuric acid was examined using scanning electron microscopy (SEM) and energy dispersive X-ray spectrometer (EDX). Cement replacement up to 20% led to a slight increase in compressive strength at 7, 28, and 120 days, while the results of durability tests showed that only up to 10% cement substitution could improve the durability of the mortar. A microstructural analysis showed that small waste grain portions in the matrix improved the whole mix density and the interfacial transition zone (ITZ) between aggregates and paste. The results of this study showed that there is an optimum replacement ratio of about 10%, beyond which the incorporation of these waste powders can cause degradation of concrete properties.
Highlights
Concrete is considered the most commonly used building material, and every year approximately 3–3.8 tonnes of concrete per person are produced worldwide [1,2]
Many researchers in the field of concrete have started to study the reduction in cement consumption by using waste and by-products in concrete production [5,6,7,8,9], as a cement replacement
supplementary cementitious materials (SCMs) are derived from by-products of various industries or natural pozzolans; their use can both improve concrete properties and help tackle some of the environmental issues in the construction industry
Summary
Concrete is considered the most commonly used building material, and every year approximately 3–3.8 tonnes of concrete per person are produced worldwide [1,2]. Red mud (RM), ground granulated blast furnace slag (GGBFS), and electric arc furnace dust (EAFD), which are generated as unwanted outcomes of bauxite and steel refineries, can be highly advantageous for concrete production, as they are mainly composed of silica (SiO2), aluminium oxide (Al2O3), ferric oxide (Fe2O3), and quicklime (CaO), respectively, making them potential pozzolans. Their grain size distribution, specific surface area, and the shape of their grains can improve the hardened and fresh concrete properties if they are mixed with cement in optimum values. Ca(OH), which is considered a by-product of cement hydration and does not contribute to the strength gain process of concrete, can react with water and GGBFS to form more calcium silicate hydrate (CSH) gel and improve hardened properties [30]
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