Sustainable Expansive Agent from FGD Gypsum and CAC Used to Mitigate Shrinkage in Alkali-Activated Mortars and Promoter the Valorization of Industrial By-Products

Thais Marques da Silva Moura () and Janaíde Cavalcante Rocha
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Thais Marques da Silva Moura: Laboratory of Waste Valorization and Sustainable Materials (ValoRes), Department of Civil Engineering, Federal University of Santa Catarina (UFSC), Florianópolis 88040-900, Brazil
Janaíde Cavalcante Rocha: Laboratory of Waste Valorization and Sustainable Materials (ValoRes), Department of Civil Engineering, Federal University of Santa Catarina (UFSC), Florianópolis 88040-900, Brazil

Sustainability, 2025, vol. 17, issue 19, 1-24

Abstract: Mineral expansive from FDG—flue-gas desulfurization—blended with calcium aluminate cement CAC was analyzed as mitigation shrinkage of alkali-activated residual mortars AAM. The AAM mortars were composed of red mud (RM) and bottom ash (BA), as precursors of a metakaolin MK-based system. MK replacement (0, 50, 70%) in alkaline solution (10M) and ratio 1:2 (binder/sand) was studied. Engineering properties were performed, and included mechanical strength, setting times, and dry shrinkage (HR 60%), as well as the microstructure formed at 7 d and 28 days. A total of 10% CAC-FGD dosage was the most efficient, reducing drying shrinkage by 23% and autogenous shrinkage by up to 30%. The findings showed that this addition also improved mechanical strength by approximately 16% at 28 days. Under the addition of CAC-FGD, the results suggest the presence of aluminosilicate gels of the (Na,C)-(A)-S-H type and the formation of ettringite, which are possibly responsible for ensuring good performance and a controlled expansion that, in turn, compensates for the shrinkage of the activated mortars.

Keywords: waste valorization; shrinkage mitigation; sustainable construction; alkali-activated mortars; expansive agent (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2025
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