Assessment of the CO₂ sequestration potential of waste concrete fines

A significant amount of CO₂ is released into the atmosphere during mining and production of construction materials, negatively affecting the environment. Reabsorption of the CO₂ into new construction materials could compensate for some of the negative impacts. This study aims to explore the CO₂ uptake capacity of waste concrete fines (WCF) and their role in lowering the environmental impact of concrete. It examines the effects of various factors such as source, composition, and grain size distribution on the CO₂ uptake capacity of WCF. The CO₂ sequestration potential and the degree of carbonation of WCF fractions were measured by thermogravimetric analysis (TGA). The results showed that the WCF from thermomechanical beneficiation had the highest CO₂ uptake, followed by the WCF from ready-mixed concrete sludge. This was due to the higher content and reactivity of calcium oxide (CaO) in these materials, which is derived from the hydrated cement paste. The WCF from different sources and processes exhibited different chemical and mineralogical compositions, which affected their CO₂ sequestration capacity. WCF showed CO₂ uptake potential ranging from 4.9 to 18.2% based on the source, size of the WCF and production method of RCA. The study suggests that CO₂ uptake by WCF could offset about 10–28% of the net carbon footprint associated with concrete production.