Potential additives for magnesia-based concrete with enhanced performance and propensity for CO2 sequestration

• Published in: Journal of CO2 utilization Vol. 56; p. 101834
• Main Authors: Dung, N.T., Unluer, C.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.02.2022
• Subjects: Additives; CO2 sequestration; MgO; Microstructure; CO2 sequestration; Additives; MgO; Performance; Microstructure
• ISSN: 2212-9820; 2212-9839
• DOI: 10.1016/j.jcou.2021.101834

•Reactive magnesia cement (RMC) concrete with hydromagnesite (H), magnesite (M) and hydration agent (HA) were investigated.•Partial replacement of RMC by H and M stimulated formation of hydrate and carbonate phases.•Use of H increased hydration, forming a bird nest-like structure containing poorly-crystalline brucite.•Combination of M and HA led to strength gain via increased carbonate content and reduced w/b ratios.•Partial replacement of RMC with M can reduce CO2 emissions and energy consumption of RMC production. This study focuses on the development of carbonated reactive magnesia cement (RMC) concrete formulations involving hydromagnesite (H), magnesite (M) and hydration agent (HA). Partial replacement of RMC by H and M stimulated the formation of hydrate and carbonate phases. Use of H increased the rate and degree of hydration, resulting in the formation of a bird nest-like structure containing poorly-crystalline brucite. The higher propensity of this poorly-crystalline phase for carbonation increased the utilisation of RMC as a binder and facilitated its conversion into strength-providing HMCs. Synergistic combination of M and HA led to significant strength gain via increased carbonate content and reduced w/b ratio. Presence of M provided micro-aggregates that facilitated the enhanced formation of large carbonate crystals with improved morphologies, resulting in microstructure densification and 113 % strength increase. Furthermore, partial replacement of RMC with M enabled reduction of natural resources, CO2 emissions and energy consumption associated with RMC production.