Development of low-carbon cement: Carbonation of compounded C2S by β-C2S and γ-C2S

Abstract

Widespread utilization of Portland cement (PC) with a large-scale carbon footprint has caused a vital climate crisis . The application of low-carbon materials rich in belite is hindered by the low hydraulic activity of C 2 S. Both β-C 2 S and γ-C 2 S can rapidly develop compressive strength and sequestrate CO 2 after carbonation . To explore the role of β-C 2 S and γ-C 2 S played on compressive strength and carbonation degree in C 2 S paste, several groups of C 2 S samples composed of pure β-C 2 S and pure γ-C 2 S in different weight contents (wt.%) were homogenized and carbonated. Compressive strength was tested, and XRD , TGA , FT-IR, and SEM analysis methods were applied to observe the carbonation properties. Experimental results showed that compressive strength positively correlated with the proportion of β-C 2 S content, and the carbonation degree positively correlated with the proportion of γ-C 2 S content. Different ratios of β-C 2 S and γ-C 2 S mainly affected the growth rates of compressive strength and carbonation degree. When β-C 2 S was 60 wt% and γ-C 2 S was 40 wt%, both compressive strength (54.4 MPa) and carbonation degree (36.7%) of carbonated samples can reach an optimum value. The calcite content increased with γ-C 2 S content, while the crystallite size of calcite decreased with the γ-C 2 S content. Through the established carbonation kinetics equation and the measured carbonation heat curves of compounded C 2 S, the possible synery effect of β-C 2 S and γ-C 2 S was proposed. Combined β-C 2 S and γ-C 2 S in cement clinker can reduce CO 2 emissions. Carbonating high-belite cement composed of a certain proportion of β-C 2 S and γ-C 2 S will contribute to developing early compressive strength and improving CO 2 sequestration of this low-carbon cementitious material .

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