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Chemical aspects on chromate in cement
Dermatosen in Beruf Und Umwelt. Occupation and Environment
|January 1, 1982
Summary
Chromate and molybdate can be incorporated into cement compounds without water extraction. Sulfate, selenate, and chromate solutions can extract these compounds, indicating substitution possibilities and limiting chromate-free cement production.
Area of Science:
- Materials Science
- Inorganic Chemistry
- Environmental Science
Background:
- Chromate compounds are present in cement clinker.
- Understanding the behavior of chromate in cement is crucial for environmental and safety assessments.
Purpose of the Study:
- To investigate the extractability of chromate and molybdate from calcium aluminate and calcium aluminate ferrite compounds.
- To determine the potential for substitution between chromate, sulfate, selenate, and molybdate in cementitious materials.
Main Methods:
- Addition of chromate and molybdate to calcium aluminate and calcium aluminate ferrite.
- Extraction experiments using water, sulfate, selenate, and molybdate solutions.
- Analysis of extractability and substitution patterns.
Main Results:
- Chromate and molybdate can be incorporated into calcium aluminate and calcium aluminate ferrite, not extractable by water.
- Sulfate, selenate, and molybdate solutions can extract approximately 2/3 of added chromate.
- Sulfate, selenate, and chromate solutions can extract approximately 2/3 of added molybdate.
- Chromate, sulfate, selenate, and molybdate exhibit substitution behavior within the cement matrix.
Conclusions:
- Chromate is partly incorporated into the crystal structures of calcium aluminate and calcium aluminate ferrite.
- The correlation between chromate and sulfate in cement is attributed to an equilibrium within and outside the crystals.
- The inherent presence of gypsum in cement limits the feasibility of producing completely chromate-free cement.