Two-step approach to manufacture sustainable artificial steel slag aggregate used in alkali-activated concrete

• Published in: Construction & building materials 2024-09, Vol.445, p.137850, Article 137850
• Main Authors: Kong, Jiafeng, Wang, Shu, Wu, Wenhao, Li, Yujiao, Chen, Mingxu, Zhou, Xiaolong, Zhang, Zuhua, Quan, Hongzhu
• Format: Article
• Language: English
• Subjects: Acid activation; Artificial aggregate; Carbonation; Microstructure; Steel slag
• ISSN: 0950-0618
• DOI: 10.1016/j.conbuildmat.2024.137850

This study utilized 3 mol/L hydrochloric acid to activate steel slag powder in combination with carbonation and produced the artificial steel slag aggregate (ASSA) for the use in alkali-activated concrete. The composition, microstructure, and properties of the ASSA were investigated. The results indicated that acid activation enhanced the compressive strength of the ASSA by 26.7 %, reduced the total porosity by 5.2 %, and facilitated the formation of portlandite, C-S-H gel, and monocarbonate in the hydration products. Carbonation enhanced the compressive strength of the ASSA by 28.5 %, reduced the total porosity by 14.5 %, and led to the formation of calcite and aragonite. The effect of acid activation coupled with carbonation on the ASSA manifested in a 43.6 % enhancement in compressive strength, a 17.9 % reduction in porosity, and an expansion rate reduction to 1.2 %. The alkali-activated concrete produced with the modified ASSA exhibited enhanced compressive strength by up to 21 % compared with the control group, facilitated internal curing to balance internal humidity, and mitigated drying shrinkage deformation. This study provides a viable and secure approach to the reutilization of steel slag. [Display omitted] •Acid activation enhanced the reactivity and volume stability of steel slag.•Calcium carbonate was calcite and aragonite in artificial steel slag aggregate.•Compressive strength was enhanced by up to 43.6 % and expansion rate was reduced to 1.2 % after modification.•Artificial steel slag aggregates mitigated drying shrinkage deformation in concrete.