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Open AccessArticle

Hydration Mechanism and Hardening Property of α-Hemihydrate Phosphogypsum

by Xianbo Li 1,2,3 and Qin Zhang 1,2,3,*
1
Mining College, Guizhou University, Guiyang 550025, China
2
National & Local Joint Laboratory of Engineering for Effective Utilization of Regional Mineral Resources from Karst Areas, Guiyang 550025, China
3
Guizhou Key Lab of Comprehensive Utilization of Nonmetallic Mineral Resources, Guiyang 550025, China
*
Author to whom correspondence should be addressed.
Minerals 2019, 9(12), 733; https://doi.org/10.3390/min9120733
Received: 25 October 2019 / Revised: 19 November 2019 / Accepted: 25 November 2019 / Published: 28 November 2019
(This article belongs to the Section Mineral Processing and Metallurgy)
The hydration and hardening of α-hemihydrate phosphogypsum (HH) prepared in the absence and presence of L-Aspartic acid (L-Asp) were investigated by thermodynamic analysis, measurements of ion concentrations and crystal water content, and morphology observation. In addition, computed tomography (CT) scanning was proposed to analyze the hole characteristic of hardened gypsum in situ. The results show that HH will pass through the unstable region and the stable region of dihydrate gypsum (DH) in turn during the hydration. The hydration of HH follows the dissolution–crystallization principle; the hydration process can be divided into the dissolution stage, dissolution–crystallization stage and equilibrium stage. Compared with the HH prepared without crystal modifier, the hydration process of HH prepared with L-Asp is obviously prolonged, and the morphology of DH changes from needle-like to diamond-shape crystals with an aspect ratio of 1:1. Meanwhile, the defect-specific surface and porosity of hardened gypsum significantly decreases, achieving a more compact, hardened paste with higher compressive strength.
Keywords: hemihydrate phosphogypsum; hydration mechanism; hardening property; computed tomography scanning; hole characteristic hemihydrate phosphogypsum; hydration mechanism; hardening property; computed tomography scanning; hole characteristic
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MDPI and ACS Style

Li, X.; Zhang, Q. Hydration Mechanism and Hardening Property of α-Hemihydrate Phosphogypsum. Minerals 2019, 9, 733.

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