Carbonation and wetting of synthetic C-S-H with Ca/Si 0.83 and 1.5

Abstract

This study explores the carbonation and wetting kinetics of synthetic calcium silicate hydrate (C-S-H) with Ca/Si ratios of 0.83 and 1.5 using in-situ X-ray diffraction (XRD), in-situ attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR), and thermogravimetric analysis (TGA). In 0.83 C-S-H, XRD results reveal pure C-S-H phases with no portlandite or CaCO₃ polymorphs, corroborating TGA findings. Minor changes suggest water incorporation. Conversely, 1.5 C-S-H exhibits distinct XRD patterns with portlandite peaks, indicating limited Ca(OH)₂ reaction. ATR-FTIR spectra confirm carbonation in both, with distinct features. 1.5 C-S-H proved to be more susceptible to carbonation due to enhanced calcium availability. Despite portlandite presence, C-S-H rapidly reacts with CO₂, likely due to its higher surface area. The study offers insights into C-S-H's carbonation behavior and structural changes during CO₂ exposure in the first 24h of reaction.