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Initial Water Adsorption Property of Manganese-Doped Belite by First-Principles Calculation

Ryoji Sakurada1, Masami Uzawa2, Yoshifumi Hosokawa3, Syun-ichiro Uchida3, Yoshiyuki Kawazoe4, Rodion Vladimirovich Belosludov5, Aaditya Manjanath6, and Abhishek Kumar Singh6

1. Dept. of Civil Engineering and Architecture, National Institute of Technology, Akita College, Akita 011-8511, Japan

2. Dept. of Safety and Environmental Engineering, Nihon University, Narashino 275-8575, Japan

3. Central Laboratory, Taiheiyo Cement Co. Ltd., Sakura 285-8655, Japan

4. New Industry Hatchery Center, Tohoku University, Sendai 980-8579, Japan

5. Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan

6. Materials Research Centre, Indian Institute of Science, Bangalore 560012, India


Abstract: The belite-rich cement makes it possible to further reduce the environmental impact of CO2 emission during manufacture of cement due to lower feed temperature of belite as compared to alite. However, belite reacts slower with water. It needs to activate the hydration reaction of belite itself. The addition of small amount of trace elements can change the inherent hydraulic activity and structural stability of belite. This study describes the numerical simulation of the effect of manganese Mn as a trace element on the initial water adsorption onto β-C2S (beta-form Belite) surface from the first-principles calculation based on density functional theory and the pseudo potential method. The surface of the β-C2S was constructed from the 2 × 1 × 2 slab forming of two β-C2S layers with a vacuum thickness of 12 Å above the super cell. One Ca(1) having seven-coordination in the second layer of β-C2S is replaced by a trace element of Mn. One H2O molecule is vertically adhered on top of Ca(1) having seven-coordination or Ca(2) having eight-coordination. Mn-doped structure of β-C2S enhances the adsorption ability of the initial H2O molecule onto Ca of belite surface as compared to pristine β-C2S without dopant. Moreover the absolute value of water adsorption energies on Ca(2) having eight-coordination are larger than that on Ca(1) having seven-coordination for Mn-doped structures. The effectiveness of the water adsorption ability by Mn-doping is lower than by Ba- and Sr-doping.

Key words: Belite, manganese atom, water adsorption, first-principles calculation.
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