Method of controlling the hydration behavior of gypsum in the manufacture of composite materials
AssigneeFraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V.
InventorsHeinz Sattler, Volker Thole, Bernhard Schmelmer
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Abstract
A method of controlling the ratio of hydration time (HT) to open time (OT) in the manufacture of composite materials from a mixture containing hydratable calcium sulphate such as gypsum binders, aggregates, fibers, water additives and other additives is disclosed. The method includes adding a retarder-accelerator combination such as Retardan and potassium sulphate to the mixture and applying pressure. The retarder-accelerator combination and application of pressure provide advantageous reduction in the ratio HT:OT. More particularly, HT:OT can be reduced to less than 1.
Claims9
A method for fabricating a gypsum composite material from a loose mixture comprising hydratable calcium sulfate having a characteristic open time (OT), aggregates, fibres, and water, said method comprising the steps of:
- adding a retarder-accelerator combination to said loose mixture, said retarder and said accelerator added in an effective amount of each to achieve the same effect as when said retarder and said accelerator are applied separately;
- applying pressure to the mixture;
- and
- hydrating the mixture during a hydration time (HT) starting at a beginning of hydration (BH) and ending at an end of hydration (EH), such that the ratio HT:OT is .ltoreq.1.
Dependencies are inferred from the claim text.