Effects of coal-ash and brewery wastewater on carbonated concrete and its carbon neutrality potential

Abstract

Concrete production is associated with environmental issues in the area of high carbon footprint of cement. The effect of Coal ash (CA) and Brewery Wastewater (BW) on concrete under prolonged accelerated carbonation curing (ACC) was assessed. It evaluated carbon sequestered by direct carbon-dioxide curing, examined the microstructure, and characterised CA and BW. Young concrete by CA and BW at 0-30% was treated to ACC in a closed carbonation chamber (post-carbonation) at a pressure of 0.3 MPa and ambient conditions for 7 days and remained in the closed chamber for an additional 21 days to achieve a stabilized curing threshold. Samples were removed and water-cured for 28 days (category 1) and non-water-cured (category 2) were analyzed for compressive strength, X-ray diffraction (XRD), and carbonation depth (d K ). The carbonation period showed visible evidence of d K using phenolphthalein. The calcite layer accounts for the improved crushing strength (CS), which surpasses the design threshold (25 MPa). Thus, CS is 29.07–37.39 MPa at 28 days. The XRD identified the main carbonation product (calcite), and d K ranged from 0.49 to 2.63 mm and 4.4 to 10.73 mm, respectively, for categories 1 and 2. ACC improved concrete with 0% CA and 20% BW, but 10% CA and 20% BW produced a more preferred result. Controlling the ACC process, CA, and BW in the correct proportions can benefit carbon neutrality in concrete.