Sulfate dispersion chromate reducer

A sulfate and reducing agent technology, used in the field of reducing chromate in cement, cement additives, and solid sulfate particles, can solve problems such as hindering tin sulfate

Inactive Publication Date: 2006-12-20
WR GRACE & CO CONN
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

This inconsistency prevents the use of tin sulfate in solution from an economic point of view

Method used

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  • Sulfate dispersion chromate reducer
  • Sulfate dispersion chromate reducer
  • Sulfate dispersion chromate reducer

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0066] Formulation of the tin sulfate composition of the present invention: tin sulfate particles (56 gm) and eutan gum base VMA (44 gm) were mixed together. The VMA is available from Grace Construction Products under the trade name V-MAR(R) 3. Other suitable VMAs may include xanthan gum, wenlai gum, and cellulose ethers, preferably dispersed in water with an optional dispersant.

[0067] Table 1 shows the performance comparison between tin sulfate solid, tin sulfate dispersion and tin sulfate solution. All additives were interground into slag cement prepared in a laboratory ball mill. In the cement prepared in the laboratory, the proportions of the various materials were as follows: 70% cement clinker, 25% slag, 2.8% gypsum, 1.9% stucco. Abrasives were prepared at ambient temperature.

[0068] The additive amounts of chromate reducing additives are shown in Table 1. Dosages of active tin sulfate moieties are also given. The soluble ppm Cr (measured as chromate) is given ...

Embodiment II

[0073] Similar experiments were carried out using cement with the following composition percentages: 95% cement clinker, 2.8% gypsum, 1.9% stucco. The respective chromate reduction properties of the samples are shown in Table 2.

[0074] Chromate Reducing Additives

Embodiment III

[0076] Another test was carried out using a cement having the following composition percentages: 65% cement clinker, 7.5% slag, 15.1% limestone, 7.5% natural pozzolan, 2.8% gypsum and 1.9% stucco, the percentages being calculated on a total weight basis. In this case, 200 ppm tin sulfate delivered in dispersion performed comparable to 300 ppm tin sulfate delivered in solution in heat treated cement. The results are shown in Table 3.

[0077] Chromate Reducing Additives

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Abstract

A chromium VI reducing composition comprising particles of solid material selected from the group consisting of iron (II) sulfate and tin sulfate, the particles being substantially uniformly dispersed within a liquid carrier. Methods for modifying hydratable cementitious materials using the chromium reducing composition are also disclosed and provide advantages over dry powder or dissolved forms of sulfate compositions when used in cement manufacturing.

Description

technical field [0001] The present invention relates to reducing agents for hexavalent chromium (VI), more particularly to cement additives, and methods for reducing chromate in cement involving solid sulfate particles dispersed in a liquid carrier. Background technique [0002] Chromium is an unavoidable trace element in the raw materials used in the manufacture of cement clinker, which is ground to make cement. In particular, hexavalent chromium ("CrVI") can be formed under the conditions of oxidation and alkali sintering in cement kilns. CrVI compounds are classified as extremely toxic because of their high oxidation potential and their ability to penetrate human tissues, causing skin sensitization, anaphylaxis and eczema. Because CrVI compounds have high solubility and are released when cement and water are mixed together, they tend to come into contact with human skin during handling of wet cement and mortar. [0003] It is desirable to reduce hexavalent chromium (CrV...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C04B7/00
Inventor L·A·贾丁C·R·科恩曼D·T·吉尔里V·古普塔全炳和
Owner WR GRACE & CO CONN
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