Properties of Dolomite Plaster Affected the by Addition of Granulated Blast-furnace Slag and Al2 (SO4) 3

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Hydrated dolomitic lime mainly composed of Ca (OH) 2 and Mg (OH) 2 is so called dolomite plaster in Japan. This is air setting and low strength, and drying shrinkage is very large. Properties of dolomite plaster were improved by addition of finery graound granulated blastfurnace slag with minor amount of anhydrous aluminium salfate. When mixture of 60-75% blastfurnace slag, 35-20% dolomite plaster and 2-3% anhydrous aluminium salfate was hydrated, the compressive strength of specimens was about 120kg/cm2 at 3 days and 150kg/cm2 at 7 days in air curing (20°C, 80% R. H.). A small amount or anhydrous aluminium salfate greatly influenced on the setting time and early strength of specimens. The strength of hardend bodies increases with increasing content of blastfurnace slag, but workability and Plasticity of paste decreased. In hydration of mixture of 50% blastfurnace slag, 47% dolomite plaster and 3% anhydrous aluminium salfate, ettringite was found as the main phase by the X-ray pawder diffraction analysis, and it was precipitated from the liquid phase as the acicular crystals.
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