Application of Ca-doped mesoporous silica to well-grouting cement for enhancement of self-healing capacity

Abstract Carbonation has been considered as an alternative to prevent CO 2 leakage. In this study, calcium-doped mesoporous silica (CDMS) was introduced into Portland cement as a promoter of carbonation. An admixture of CDMS and American Petroleum Institute (API) Class G Portland cement exposed to CO 2 -saturated water was analyzed under geologic sequestration conditions (40 °C and 80 MPa) to assess the carbonation properties and self-healing effect of CDMS for CO 2 storage. The capacity of CDMS to synthesize CaCO 3 from CO 2 via carbonation was identified in an in vitro crystallization test. Analysis of the cut surface of a cement core showed the rapid synthesis of CaCO 3 including calcite and aragonite. Rietveld analysis was employed for quantitative phase analysis. The quantitative analysis of the cement carbonation showed that tricalcium silicate (C 3 S) and dicalcium silicate (C 2 S) play important roles in cement carbonation. Several crystal phases of CaCO 3 were identified in this study including calcite, aragonite and amorphous CaCO 3 . X-ray diffractometry (XRD), a field emission-scanning electron microscope (FE-SEM) equipped with an energy dispersive X-ray spectrometer (EDS), 29 Si MAS-NMR (magic angle spinning–nuclear magnetic resonance) spectrometry, thermogravimetry-differential thermal analysis (TG-DTA) and FT-IR (Fourier transform infrared spectroscopy) were applied to characterize the admixture.