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.