The coupled reaction and crystal growth mechanism of tricalcium silicate (C3S): An experimental study for carbon dioxide geo-sequestration wells

Based on the decades of studies and commercial experiments, the geo-sequestration of carbon dioxide (CO2) has been the most efficient way to solve the green gas emission problem for the world. As the vital barrier of the sequestration well, the cement shell must be credible and durable until the well is abandoned. To date, some of sequestration projects have operated for many years, however, CO2 leakage has been a major threat in these projects. Although, ordinary Portland cement (OPC) is widely used in these projects, it has been found to be unstable in acidic environments. To assess these potential risks, this study combines cement hydration and carbonation as a coupled reaction to study the cement at an early age. OPC contents are too complex to study, thus, the main phase of C3S in the OPC was assessed in the CO2 environment. The experimental results indicate that the coupled reaction was considerably different from that in a previous study. In regard to the hydration reaction, cement slurry may provide the leakage pathway for sequestered CO2. In addition, the carbonation product is composed of an unstable crystal, which has proved to dissolve during long-lasting experiments. (C) 2018 Elsevier Ltd. All rights reserved.