Effect of Alkaline Salts on Calcium Sulfoaluminate Cement Hydration
Luís Urbano D. Tambara Júnior,
Janaíde C. Rocha,
Malik Cheriaf,
Pilar Padilla-Encinas,
Ana Fernández-Jiménez,
Angel Palomo
Affiliations
Luís Urbano D. Tambara Júnior
Laboratory of Waste Valorization and Sustainable Materials (ValoRes), Department of Civil Engineering, Federal University of Santa Catarina (UFSC), Florianópolis 88040900, Brazil
Janaíde C. Rocha
Laboratory of Waste Valorization and Sustainable Materials (ValoRes), Department of Civil Engineering, Federal University of Santa Catarina (UFSC), Florianópolis 88040900, Brazil
Malik Cheriaf
Laboratory of Waste Valorization and Sustainable Materials (ValoRes), Department of Civil Engineering, Federal University of Santa Catarina (UFSC), Florianópolis 88040900, Brazil
Pilar Padilla-Encinas
Eduardo Torroja Institute, National Research Council (CSIC), 28033 Madrid, Spain
Ana Fernández-Jiménez
Eduardo Torroja Institute, National Research Council (CSIC), 28033 Madrid, Spain
Angel Palomo
Eduardo Torroja Institute, National Research Council (CSIC), 28033 Madrid, Spain
This work analyzes the effect of the presence of 5 wt.% of solid sodium salts (Na2SO4, Na2CO3, and Na2SiO3) on calcium sulfoaluminate cement (CSA) hydration, addresses hydration kinetics; 2-, 28-, and 90-d mechanical strength, and reaction product microstructure (with X-ray diffraction (XRD), and Fourier transform infrared spectroscopy, (FTIR). The findings show that the anions affect primarily the reactions involved. Ettringite and AH3, are the majority hydration products, while monosulfates are absent in all of the samples. All three salts hasten CSA hydration and raise the amount of ettringite formed. Na2SO4 induces cracking in the ≥28-d pastes due to post-hardening gypsum and ettringite formation from the excess SO42– present. Anhydrite dissolves more rapidly in the presence of Na2CO3, prompting carbonation. Na2SiO3 raises compressive strength and exhibits strätlingite as one of its reaction products.
