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Home > Publications > International Concrete Abstracts Portal
The International Concrete Abstracts Portal is an ACI led collaboration with leading technical organizations from within the international concrete industry and offers the most comprehensive collection of published concrete abstracts.
Title: Absorption and Hydration Behavior of Tricalcium Aluminate-Water and Tricalcium Aluminate-Gypsum-Water Systems in the Presence of Superplasticizers
Author(s): V. S. Ramachandran
Publication: Journal Proceedings
Appears on pages(s): 235-241
Keywords: adsorption; calcium aluminate hydrates; calorimeters; conductivity; C3A; ettringite;gypsum; hydration; melamine resins; napthalene compounds; plasticizers; sulfonation.
Abstract:Additions of I, 2, and 4 percent sulfonated melamine or naphthalene formaldehyde retard the hydration of C,A and the rate of conversion of hexagonaf to cubic aluminate hydrate. This effect is more pronounced at high dosages of the superplasticizer. Rate of adsorption of the superplasticizer is higher in the CA-H,0 system than in the hexagonal or cubic phase; adsorption is irreversible. In a non-aqueous medtum only the hexagonal phase adsorbs small amounts of superplasticizer. Reaction between tricalcium aluminate and gypsum to form ettringite is accelerated in the presence of superplasticizer. The exothermal reaction occurring in this system as a result of the reaction of excess tricalcium aluminate b delayed in the presence of the superplasticizer. Adsorption experiments on the tricalcium aluminate-gypsum mixture prehydrated for different periods show that the rate of adsorption is generally in the decreasing order 0, I hr. 2 days, I5 min, 30 min, and 5 min. In the non-aqueous medium only small amounts of superplasticizer are adsorbed. Adsorption was irreversible in all cases.
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