Premium
Autoclaved gypsum plaster from selenite and by‐product phosphogypsum
Author(s) -
Singh Manjit,
Rai Mohan
Publication year - 1988
Publication title -
journal of chemical technology and biotechnology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.64
H-Index - 117
eISSN - 1097-4660
pISSN - 0268-2575
DOI - 10.1002/jctb.280430102
Subject(s) - phosphogypsum , gypsum , hemihydrate , autoclave , materials science , crystallinity , mineralogy , anhydrite , calcination , metallurgy , composite material , chemistry , raw material , biochemistry , organic chemistry , catalysis
Abstract Investigations were carried out to produce an autoclaved gypsum plaster (α‐hemihydrate) by heating the naturally occurring selenite and by‐product phosphogypsum under steam pressure in an autoclave. Various factors effecting the calcination of gypsum such as pressure, time of the autoclaving process and the particle size of gypsum lumps were investigated. The formation of hemihydrate was examined by periodic differential thermal analysis and weight loss determinations. The mineralogical studies of plaster were determined using microscopy and X‐ray diffraction. The data showed that complete inversion of gypsum into hemihydrate takes place by heating gypsum of particle size 15 to 20 mm 3 at 1.75 kg cm −2 steam pressure for 7 h. The microscopy of plaster revealed formation of well‐defined euhedral prismatic and tabular shaped crystals showing a higher degree of crystallinity than the conventional β‐hemihydrate. The hydraulic properties of plaster were studied and it was found to possess considerable strength (230 kg cm −2 ). The α‐plaster has been found suitable for making masonry mortar and fibrous plaster boards according to the relevant Indian Standards for use in construction works.