Bauhaus-Universität Weimar

Additive-dependent effects
on plaster hydration

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1 “GYP-LABO” test setup by Bold-Technoconsult

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2 A filled FIB/WdB shrinkage drain

3 Temperature curves for the hydration of plaster of Paris with different additives

4 Measured linear change during hydration of plaster of Paris with different additives

5 Strength values of standard prisms containing different additives/combined additives

The purpose of this work was to illuminate the effects of certain additives or of combined additives on a hydrating gypsum plaster. The changes in hydration and the strength development process are described in particular.

1 Introduction

Among calcium sulphate binders, building plasters in particular, plaster of Paris, or gypsum plaster, is the most well-known and often used. Plaster of Paris is a partially calcined product of raw gypsum (CaS0₄ · 2 H₂O) resulting from exposure to temperatures of 120-180 °C in a firing system. In comparison with other calcium sulphate binders, plaster of Paris is relatively inexpensive to produce and is therefore turned out at high tonnage rates. The main constituent of plaster of Paris is calcium sulphate hemihydrate (CaS0₄ · 0.5 H₂O [HH]) in its β form. β-HH has a...

TEXT Tabea von Bronk M.Sc., Dr.-Ing. Hans-Bertram Fischer, Bauhaus-Universität Weimar, F.A. Finger Institute for Building Material Engineering, Weimar/Germany