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Preparation and Reaction Mechanism Characterization of Alkali-activated Coal Gangue–Slag Materials

School of Mechanics and Civil Engineering, China University of Mining and Technology (Beijing), Beijing 100083, China
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Materials 2019, 12(14), 2250; https://doi.org/10.3390/ma12142250
Received: 7 June 2019 / Revised: 9 July 2019 / Accepted: 10 July 2019 / Published: 12 July 2019
(This article belongs to the Special Issue Concrete and Construction Materials)
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Abstract

In this paper, slag is used as a calcium source to make alkali-activated coal gangue–slag (AACGS) based material. The reaction mechanism of AACGS materials was discussed in depth by means of XRD, FT-IR, 29Si MAS-NMR (nuclear magnetic resonance) and SEM-EDS (energy dispersive spectrometer). The experimental results show that coal gangue can be used as a raw material for preparing alkali-activated materials. The liquid–solid ratio is the most influential factor on AACGS paste fluidity and strength, followed by slag content. As the modulus of sodium hydroxide increases, the depolymerization process of the reactant precursor is accelerated, but the high sodium hydroxide concentration inhibits the occurrence of the early coal gangue–slag polycondensation reaction, and exerts little effect on the 28 d compressive strength. Ca2+ in the slag promotes exchange with Na+, and the product is converted from N-A-S-H gel to C-(A)-S-H gel, and C-(A)-S-H is formed with higher Ca/Si ratio with the increase of slag content. The slight replacement of coal gangue by slag can greatly improve the reaction process and the strength of AACGS materials. View Full-Text
Keywords: alkali-activated coal gangue–slag; paste fluidity; cement paste fluidity; compressive strength; polycondensation reaction alkali-activated coal gangue–slag; paste fluidity; cement paste fluidity; compressive strength; polycondensation reaction
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Ma, H.; Zhu, H.; Yi, C.; Fan, J.; Chen, H.; Xu, X.; Wang, T. Preparation and Reaction Mechanism Characterization of Alkali-activated Coal Gangue–Slag Materials. Materials 2019, 12, 2250.

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