Environmental-Friendly Mortar Produced with Treated and Untreated Coal Wastes as Cement Replacement Materials

Abstract

This study aims to examine the influence of untreated coal waste (UCW) and treated coal waste (TCW) as supplementary cementitious materials (SCMs) on the environmental, mechanical, durability, and microstructural characteristics of mortar mixes. UCW preparation procedure consists of sequential steps of crushing and grinding. Afterward, UCW is thermally activated through incinerating at 750°C to be promoted to TCW. Experimental work includes mixing mortar mixtures by partially replacing cement with the coal waste binders (UCW and TCW) at different incorporation levels of 4, 8, 12, and 16% of cement weight. Toxicity characteristic leaching procedure (TCLP) test was applied to investigate the environmental impacts of coal wastes. TCLP test results pointed out that heavy metals including Manganese, Cadmium, Lead, and Chromium could successfully entrap in the cement matrix. The compressive and flexural strengths as mechanical characteristics of mortar mixtures were determined at 3, 7, 28, 90, and 180 curing days. Moreover, the mortar specimens were immersed in 3% sulfuric acid (H2SO4) for 60 and 150 days. Durability results showed that the H2SO4 attack resistance of binary cement mortars containing 4% coal waste binders was better than the plain mortar. Based on the scanning electron microscopy (SEM) images, ettringite was found as the main hydration product of binary cement after 28 days; however, the existence of calcium silicate hydrate (CSH) and calcium hydroxide (Ca(OH)2) in the cement matrix of mixes after 90 days explains the more compact microstructure attained by using coal waste as cement replacement materials compared to control mixtures.

Modelling of fresh properties and strength activity index with microstructure characterisation of ternary cement incorporating waste glass and granulated blast furnace slag

“…Several industrial wastes have been successfully used as SCMs, including fly ash, waste glass, marble waste, cement kiln dust, and granulated blast furnace slag [4][5][6][7]. Partially replacing cement with these waste materials has both ecological and economic impacts, offering a sustainable and environmentally friendly solution that conserves natural resources [8]. Among these added wastes, granulated blast furnace slag (GBS) is a by-product generated from the production of iron and steel, which is removed from the blast furnace in steam or water, dried, transformed into granules, and processed into a powder in a ball mill.…”