Evaluation of the long-term compressive strength development of the sewage sludge ash/metakaolin-based geopolymer

• Published in: Materiales de construcción (Madrid) 2021-07, Vol.71 (343), p.e254
• Main Authors: Istuque, D., Soriano, L., Borrachero, M.V., Payá, J., Akasaki, J.L., Melges, J.L.P., Tashima, M.M.
• Format: Article
• Language: English
• Subjects: Alkali-activated cement; Ashes; Catalytic cracking; Cement; Compressive strength; Curing; Density; Geopolymers; Metakaolin; Microstructure; Mortar; Mortars (material); Pastes; Raw materials; Scanning electron microscopy; Sewage sludge; Sludge; Temperature; Water treatment
• ISSN: 0465-2746; 1988-3226
• DOI: 10.3989/mc.2021.13220

This paper aimed to evaluate the long-term compressive strength development of the sewage sludge ash/metakaolin (SSA/MK)-based geopolymer. SSA/MK-based geopolymeric mortars and pastes were produced at 25ºC with different SSA contents (0 - 30 wt.%). Compressive strength tests were run within the 3-720 curing days range. A physicochemical characterisation (X-ray diffraction and scanning electron microscopy) was performed in geopolymeric pastes. All the geopolymeric mortars presented a compressive strength gain with curing time. The mortars with all the SSA evaluated contents (10, 20, 30 wt.%) developed a compressive strength over 40 MPa after 720 curing days at 25ºC. The maximum compressive strength of the mortars with SSA was approximately 61 MPa (10 wt.% of SSA), similarly to the reference mortar (100% MK-based geopolymer). The microstructure analyses showed that the SSA/MK-based geopolymer presented a dense microstructure with N-A-S-H gel formation.