Objective
The aim of the research is to provide qualitative and quantitative insight into the underlying phenomena of strength and durability of both pure gypsum and gypsum reacted with pozzolanic materials.
Such a basic materials science knowledge is required for an expansion of gypsum applications in the building industry.
It has been shown that it is possible to produce compacted gypsum with a low porosity and a high strength on a laboratory scale by uniaxial compaction of flue gas desulphurization (FGD) gypsum powder. Compacted FGD gypsum cylinders were produced at a compaction pressure between 21% and 6% by volume and having a compressive strength between 20 and 96 MPa. Compaction of dry gypsum powder was not successful. It is necessary to add, dependent on compaction pressure, a few per cent of water to achieve suitable density and strength properties.
Notably the microstructure of compacted gypsum is completely different to that of cast gypsum. While cast gypsum consists of a network of intergrown fine acicular crystals, in compacted gypsum coarse granular crystals are aligned boundary to boundary without much intergrowth. Microstructural examinations showed that an increase in compaction pressure causes better boundary to boundary packing, preferred orientation of grains perpendicular to the compaction direction, breaking of grains and an increase in grain deformation which was indicated by microcracking and undulatory extinction.
Fields of science
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2288 GH RIJSWIJK
Netherlands