UNIVERSITY OF SIEGEN

Investigations of the hydration of calcium sulfate hemihydrate

The application of calcium sulphate based binders need different properties, which are influenced by the morphology of the dihydrate crystals, and which depend on applied additives, reaction temperature or the production conditions of the reactant hemihydrate. The results show first only hemihydrate which is dissolved and the retarding period starts. Seed crystals of dihydrate are formed subsequently during the next few minutes.

1 Introduction

Gypsum is one of the most used materials in the world; 119 million tons of natural gypsum were extracted worldwide in 2006 (MINERAL COMMODITY 2007). Additionally another 200 million tons of byproduct gypsum came from different processes like phosphoric acid, citric acid or hydrogen fluorine production or from flue gas desulfurization.

Calcium sulphate based binders and gypsum are used for very different technical applications like floor pavement, stucco or plaster board in the building industry, for casting in the ceramic industry, as an additive in polymers or in colors or for...

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