Effect of sodium hydroxide on the carbonation behavior of β-dicalcium silicate

Carbonation of industrial solid wastes containing calcium silicate can reduce CO2 emissions as well as produce useful building materials. However, until a fully understanding of the hardening and solidification mechanism of solid wastes is obtained, their utilization in engineering applications may remain limited. In respect of this, the present work examined the effect of sodium hydroxide (NaOH) on the carbonation degree and carbonation products structure of β-dicalcium silicate (β-C2S) by using the X-ray diffraction (XRD), Fourier transform infrared spectrometer (FT-IR) and scanning electron microscopy (SEM-EDS), respectively. Moreover, the soluble sodium ions content and pH values of samples suspension were also monitored by using a five channel flame photometer and a digital pH meter, respectively. The results indicated that sodium hydroxide was adverse to the carbonation of β-C2S. In the presence of NaOH, stabilized vaterite phase was formed and the polymerization degree of silicon dioxide gels was also decrease. In turn, soluble sodium ions could be solidified in vaterite crystal structure and the pH values after carbonation was also decreased, providing a new insight into potential means to utilize alkaline solid wastes by carbonation, safely.