Title:
Role of Intercrystallite Phosphorus on Properties of α-Hemihydrate Gypsum
Author(s):
Dongmei Liu, Xinyu Li, Wanqing Zhou, Gang Xu, and Yi Qin
Publication:
Materials Journal
Volume:
122
Issue:
4
Appears on pages(s):
57-66
Keywords:
α-hemihydrate gypsum; hydration; intercrystalline phosphorus; microstructure; morphology; setting time; strength
DOI:
10.14359/51746806
Date:
7/1/2025
Abstract:
Phosphogypsum (PG) is often used to produce α-hemihydrategypsum (α-HH), but the impurities in PG, including intercrystallinephosphorus (IP), limit its reuse. The objective of this paper isto study the effect of IP on the morphology, hydration, and hardening properties of α-HH, using X-ray diffraction (XRD); X-rayphotoelectron spectroscopy (XPS); scanning electron microscopy(SEM); Fourier-transform infrared spectroscopy (FTIR); andtesting of setting time, hydration, heat, and strength. The resultsrevealed that IP dissolved out from dihydrate gypsum (DH) andentered the lattice of α-HH during the preparation of α-HH, whilethere was little difference in the morphology of α-HH. When α-HHhydrated, IP dissolved and converted into Ca3(PO4)2 absorbed onthe surface of DH. 0.04% IP had no effect on the hydration, settingtime, and strength of α-HH, with 0.1% or more IP significantlyprolonging the hydration of α-HH and deteriorating microstructureof hardened paste, thus reducing strength. Based on the results, IPcontent in PG should be controlled to less than 0.04%.