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Cement clinker with low CO2 emission was prepared in laboratory, which mainly consist of belite (C2S), calcium sulfoaluminate (C4A3S), and ferrite (C4AF). The mineral composition of clinker was optimized for better compressive strength development. The chemical and physical properties of this prepared cement were characterized through X-ray diffraction (XRD), back scattered electron-scanning electron microscopy (BSE-SEM) and differential thermal analysis (DTA). The results reveal that C4A3S governs most of the compressive strength at early ages, while C2S contributes to the later strength development. C4AF is in liquid when fired to 1300°C, beneficial to the mass transfer but causing high crystallinity of C2S when excessive. Finally the results of experiments suggest that the optimal composition of clinker is 50wt. % C2S, 40wt. % C4A3S and 10wt. % C4AF.

Portland cement production leads to significant carbon dioxide emission and greenhouse effect. Magnesium oxide eco-cement, which is a mixture of Portland cement, magnesium oxide and fly ash, may be an alternative production. In this paper, the issue is focused on the carbon dioxide absorption ability and mechanical performance of this eco-cement. Several mix proportions of eco-cement were designed to conduct forced carbonation, strength and expansion tests. Also, microstructure analysis after carbonation was conducted. The results indicate that magnesium oxide eco-cement can efficiently absorb carbon dioxide and carbonation can improve mechanical performance substantially, also expansion of the eco-cement is found to fall within the safe limits and possesses good stability and soundness.