Coupling effect of γ-dicalcium silicate and slag on carbonation resistance of low carbon materials

Abstract

In this paper, the combined use of γ-dicalcium silicate and slag for possible coupling effect on carbonation resistance was investigated. The potential of the use of γ-C2S to impart carbonation immunity to slag blended materials at early age has not been fully explored so far. In this regard, 15, 30 and 50% slag blended cement paste and mortar samples containing 0, 5, 10, 15, 20% of γ-C2S in replacement of cement were manufactured before undergoing accelerated carbonation for 3, 7 and 28 days. Then, techniques of X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA) and Mercury Intrusion Porosimetry (MIP) were utilized to analyze the carbonation characteristics. Results show that the carbonation of γ-C2S in the presence of slag is effective in CO2 sequestration, pore refinement and surface hardening. Moreover, an optimum combination of γ-C2S and slag exists for achieving the smallest carbonation depth which is 78% lower than the observed maximum, from which certain coupling effect was identified. Lastly, a conceptual model was presented to probe into the mechanism. Such research shall be conducive to the search for next-generation low carbon concrete with improved durability.