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Materials 2019, 12(1), 163; https://doi.org/10.3390/ma12010163

Influence of α-Calcium Sulfate Hemihydrate on Setting, Compressive Strength, and Shrinkage Strain of Cement Mortar

1
Mineral Resources Research Division, Korea Institute of Geoscience and Mineral Resources, Daejeon 34132, Korea
2
Department of Architectural Engineering, Chungnam National University, Daejeon 34134, Korea
3
RDM Industrial Development Co., Ltd., Daejeon 34831, Korea
4
Corporate Research Institute, Yusung-Tech Co., Ltd., Okcheon 29057, Korea
5
Department of Architecture and Urban Design, Kyushu University, Fukuoka 812-0053, Japan
*
Author to whom correspondence should be addressed.
Received: 4 December 2018 / Revised: 27 December 2018 / Accepted: 2 January 2019 / Published: 7 January 2019
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Abstract

This study focused on the quick initial setting time and the expansion strain that occurs during the early aging of α-calcium sulfate hemihydrate (αHH) and examined the setting, compressive strength, and shrinkage strain of αHH-replaced cement mortar. The results show that the initial setting time significantly decreased with an increase in the αHH replacement ratio. Drastic occurrence of ettringite was observed early in the aging of cement mortar when αHH was substituted into the cement; however, the ettringite was not converted to monosulfate with increasing age and thus was not favorable for the development of the compressive strength. When αHH was substituted into cement, using Portland blast-furnace slag cement (PSC) was more advantageous than using ordinary Portland cement (OPC) for the development of the compressive strength. Meanwhile, the expansion of early age αHH can decrease the shrinkage strain of cement mortar. The generation of ettringite is more effective when αHH is substituted into PSC than into OPC and is thus more effective in suppressing the shrinkage strain. View Full-Text
Keywords: α-calcium sulfate hemihydrate; cement mortar; ettringite; initial setting time; compressive strength; shrinkage strain α-calcium sulfate hemihydrate; cement mortar; ettringite; initial setting time; compressive strength; shrinkage strain
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Lee, B.; Kim, G.; Nam, J.; Lee, K.; Kim, G.; Lee, S.; Shin, K.; Koyama, T. Influence of α-Calcium Sulfate Hemihydrate on Setting, Compressive Strength, and Shrinkage Strain of Cement Mortar. Materials 2019, 12, 163.

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