Recycling of red mud and flue gas residues in geopolymer aggregates (GPA) for sustainable concrete

• Published in: Resources, conservation and recycling Vol. 191; p. 106893
• Main Authors: Qian, Lan-Ping, Ahmad, Muhammad Riaz, Lao, Jian-Cong, Dai, Jian-Guo
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.04.2023
• Subjects: Flue gas residues (FGR); Geopolymer aggregate concrete (GAC); Geopolymer aggregates (GPA); Mechanical properties; Red mud (RM); Mechanical properties; Geopolymer aggregates (GPA); Red mud (RM); Flue gas residues (FGR); Geopolymer aggregate concrete (GAC)
• ISSN: 0921-3449; 1879-0658
• DOI: 10.1016/j.resconrec.2023.106893

•Red mud (RM) and flue gas residue (FGR) partially replaced precursor and activator.•Replacement rate of fly ash by RM and Na2O in activator by FGR reached 40% and 32%.•RM and FGR had minimal impacts on compressive strength of GPA pastes.•Concrete strength declined by 13.4% upon 100% replacement of NA by GPA. This study proposed simultaneous utilization of red mud (RM) and flue gas residues (FGR) as a partial replacement of traditional precursors and energy-intensive activators. Reaction mechanisms of geopolymer pastes were investigated through isothermal calorimetry, X-ray diffraction, thermogravimetry and infrared spectroscopy, by varying the dosage of RM (40%) and FGR (24%, 32%). Results showed that use of RM and FGR as a replacement of FA and commercial activator had a limited influence on the compressive strength. RM and FGR participated in reaction at a slower rate. After optimization, heat-cured FGR0.32 mix was selected to manufacture geopolymer aggregates (GPA). Engineering properties, cost analysis and environmental impact of GPA were evaluated. Natural aggregates (NA) were replaced by GPA at replacement levels of 25%, 50%, 75% and 100% by volume to prepare concrete. GPA concrete with 25% and 100% replacement level could achieve the 94.6% and 86.6% of NA concrete strength respectively at 28 days age. [Display omitted]