An NMR Spectroscopic Investigation of Aluminosilicate Gel in Alkali-Activated Fly Ash in a CO₂-Rich Environment

• Published in: Materials Vol. 9; no. 5; p. 308
• Main Authors: Park, Sol-Moi, Jang, Jeong-Gook, Chae, Seen-Ae, Lee, Haeng-Ki
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 26.04.2016; MDPI
• Subjects: alkaline activation; Aluminosilicates; Aluminum silicates; Binding; Carbon dioxide; Carbonation; Chemistry; Curing; Exposure; Fly ash; geopolymer; Investigations; NMR; NMR spectroscopy; Nuclear magnetic resonance; Silicon; geopolymer; fly ash; alkaline activation; NMR spectroscopy; carbonation
• ISSN: 1996-1944; 1996-1944
• DOI: 10.3390/ma9050308

The present study investigated aluminosilicate gel in alkali-activated fly ash exposed to a CO₂-rich environment by means of NMR spectroscopy. The alkali-activated fly ash was exposed to an atmospheric CO₂ concentration of 10% after curing at 80 °C initially for 24 h. Under high concentrations of CO₂, highly reactive components Na and Al, which completely reacted within the first few hours, were unaffected by carbonation, while Si, with relatively slower reactivity, behaved differently. Despite a lower degree of the reaction in the carbonated sample, the monomeric silicates rapidly became of higher polymerization, meaning that exposure to high concentrations of CO₂ caused Si to form a binding gel phase. Consequently, the carbonated sample possessed a higher amount of binding gel. The obtained results may be useful to understand the fundamental chemistry and behavior of aluminosilicate gel under high concentrations of CO₂.