The Synthesis of α-C₂S Hydrate Substituted with Al³⁺ Ions in Mixture with CaO/SiO₂ = 1.75

Abstract:

The parameters of α-C₂SH substituted with Al³⁺ ions hydrothermal synthesis was determined. α-C₂SH was synthesized in the primary mixtures with CaO/(SiO₂+Al₂O₃) = 1.75 and Al₂O₃/(SiO₂+Al₂O₃) = 0; and 0.025. The hydrothermal synthesis has been carried out in unstirred suspensions under saturated steam pressure in argon atmosphere at 175 °C temperature for 4; 8; 16; 24; 48; 72 hours by applying extra argon gas (10 bar). It was determined that in unstirred CaO–SiO₂·nH₂O–H₂O suspensions, the additive of Al₂O₃ changes the formation mechanism of synthesis products as well as their stability during the isothermal curing. It should be noted that in the mixtures with Al₂O₃, within 4 hours of isothermal curing at 175 °C all Al³⁺ ions were incorporated in the synthesis products structure. However, Al₂O₃ additive has negative influence on the formation of calcium silicate hydrates because even after 24 h of isothermal curing quite intensive diffraction peaks of unreacted portlandite were identified. When hydrothermal synthesis is extended to 48 hours, Ca (OH)₂ fully reacted and dibasic calcium silicate hydrates start dominate in the products.

• Periodical: Solid State Phenomena (Volume 244)
• Pages: 26-33
• DOI: https://doi.org/10.4028/www.scientific.net/SSP.244.26
• Online since: October 2015
• Authors: Kęstutis Baltakys*, Tadas Dambrauskas, Anatolijus Eisinas
• Keywords: Calcium Silicate Hydrate (C-S-H), Hydrothermal Synthesis, α-C₂S Hydrate

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