Showing papers on "Ettringite published in 1977"
TL;DR: In this paper, the influence of gypsum content on the hydration and compressive strengths was studied on two commercial Portland cements having the same amount of alite, a similar amount of C3A, but different amounts of readily soluble alkalies and sulfates.
38 citations
Patent•
11 Apr 1977
TL;DR: In this article, the ettringite forming reaction was used to make tri-and hexavalent Cr insoluble and cake it, and aluminous sources such as slaked lime, gypsum, Kanto laom, etc.
Abstract: PURPOSE:In treating waste containing tri-and hexavalent Cr, by using ettringite forming reaction, aluminous sources such as slaked lime, gypsum, Kanto laom, etc. are added to make Cr insoluble and cake it.
6 citations
TL;DR: Quartz surfaces counteract the retarding action of SO42-on the hydration of C3A, by presenting additional sites for ettringite crystallization as discussed by the authors, which can influence the local concentrations there.
6 citations
Patent•
27 Oct 1977
TL;DR: In this article, the authors proposed a method for the formation of ettringite fibres by addn. of water in such an amt. that the prod. contains is not > 25% solids and carrying out the reaction with continuous stirring at 1-5 times the intensity needed to maintain a homogeneous suspension.
Abstract: Prodn. of ettringite (3CaO.Al2O3.3CaSO4.32H2O) involves the simultaneous hydration of a stoichiometric mixt. of Ca aluminate and Ca sulphate at 20-90 degrees C with water in at least the stoichiometric amt. and not more than the amt. giving a prod. contg. 5 wt.% ettringite (dry) and 95 wt.% water. The stoichiometry is defined by >=1 of 5 specified equations. Quicklime or slaked lime is added in an amt. liberating Ca++ ions giving the stoichiometric equilibrium for ettringite formation, as in the parent patent. The improvement comprises formation of ettringite fibres by addn. of water in such an amt. that the prod. contains is not >25% solids and carrying out the reaction with continuous stirring at 1-5 times the intensity needed to maintain a homogeneous suspension. The original process is extended to allow the prodn. of fibres, e.g. 1-350 mu m long. These can be used as (partial) substitute for asbestos fibres, e.g. for the prodn. of asbestos cement materials or coatings or binders for refractories; and in the form of aggregates as catalyst supports and in the prodn. of thermal and acoustic insulation. The fibres have good refractory properties.
5 citations
04 Mar 1977
TL;DR: Using scanning electron microscopy, the development of the hydration products of a cement with and without calcium lignosulfonate (CLS) admixture was followed as discussed by the authors.
Abstract: Using scanning electron microscopy, the development of the hydration products of a cement with and without calcium lignosulfonate (CLS) admixture was followed. The hydration was observed over the period from 4 hours up to 28 days. It was concluded that the presence of CLS did not change the morphology and structure of the hydration products compared to admixture free hydrates. The basic structure is mainly ettringite rods and clusters of calcium silicate hydrate (CSH) fibers. This basic structure becomes denser as hydration proceeds.
4 citations
Patent•
29 Mar 1977
TL;DR: In this article, a process for synthesizing ettringite of high degree of crystallinity and easily crystallizable was proposed, which is a process that is suitable for high temperature and high humidity.
Abstract: PURPOSE:Process for synthesizing ettringite of high degree of crystallinity and is easily crystallizable.
1 citations
TL;DR: In this paper, the effects of chromium-containing clinker minerals on the early hydration of portland cements were investigated, and it was shown that the Ca(OH)2 and ettringite crystals formed during hydration grew thicker than those in cement pastes lacking the ion.
Abstract: Readily water-soluble, chromium-containing phases exist among the principal clinker minerals of a superhigh-early-strength portland cement manufactured by adding small amounts of chromium, manganese, and fluorine to the cement raw mix. The effects of these phases on the early hydration of the cement were investigated. The phases dissolve in the mixing water and release K+, Na+, CrO42-, and SO42- into the liquid phase. Because of the presence of CrO42-, the Ca(OH)2 and ettringite crystals formed during hydration grew thicker than those in cement pastes lacking the ion. This growth behavior enhances the early mechanical strength of the cement.