Microstructural characterization of CO2-cured calcium silicate cement

Abstract

Calcium silicate cement (CSC) is a non-hydraulic cement that solidifies in moist conditions with CO₂ curing. To contribute to the standardization of CSC, the material has been produced locally, and the microstructural characterization of the carbonation products of CSC samples with water-to-cement (W/C) ratios of 0.35, 0.4 and 0.45 at 10% CO₂ concentration using XRD, ²⁹Si MAS NMR, ¹H NMR and compressive strength tests. CSC primarily consists of Q⁰, Q¹ and Q² silica species, among which β-C₂S and β-CS exhibit higher reactivity to CO₂ curing. The obtained results confirm the presence of calcite and amorphous phases as the main carbonation products, which become more prominent with an elapse in CO₂ curing. The CO₂ uptake of CSC samples with a W/C ratio of 0.45 was 8 g per 100 g binder, although a higher W/C ratio induced a relatively larger capillary and gel pore width, consequently reducing the strength of CSC.