Chromium behavior during cement-production processes: A clinkerization, hydration, and leaching study
► Behavior of chromium during cement-production processes. ► Formation of new chromium compounds in clinker with chromium oxidation states of +3, +4.6, +5, and +6. ► Addition of chromium altered the composition of the clinker phases, setting time, and compressive strength of hydrated mixes. ► Cr 3+...
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Published in | Journal of hazardous materials Vol. 191; no. 1; pp. 296 - 305 |
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Main Authors | , , , |
Format | Journal Article |
Language | English |
Published |
Kidlington
Elsevier B.V
15.07.2011
Elsevier |
Subjects | |
Online Access | Get full text |
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Summary: | ► Behavior of chromium during cement-production processes. ► Formation of new chromium compounds in clinker with chromium oxidation states of +3, +4.6, +5, and +6. ► Addition of chromium altered the composition of the clinker phases, setting time, and compressive strength of hydrated mixes. ► Cr
3+ and Cr
6 were leached during leaching tests, whereas other species remained in the mortar.
The behavior of chromium during the production of cement clinker, during the hydration of cement and during the leaching of cement mortars was investigated. The microstructures of clinker and mortar properties were investigated using free lime, XRD, SEM/EDS, and TG/DTA techniques. Chromium was found to be incorporated in the clinker phase. The formation of new chromium compounds such as Ca
6Al
4Cr
2O
15, Ca
5Cr
3O
12, Ca
5Cr
2SiO
12, and CaCr
2O
7, with chromium oxidation states of +3, +4.6, +5, and +6, respectively, was detected. After the hydration process, additional chromium compounds were identified in the mortar matrix, including Ca
5(CrO
4)
3OH, CaCrO
4·2H
2O, and Al
2(OH)
4CrO
4, with chromium oxidation states of +4.6, +6, and +6, respectively. Additionally, some species of chromium, such as Cr
3+ from Ca
6Al
4Cr
2O
15 and Cr
6+ from CaCr
2O
7, CaCrO
4·2H
2O, and Al
2(OH)
4CrO
4, were leached during leaching tests, whereas other species remained in the mortar. The concentrations of chromium that leached from the mortar following U.S. EPA Method 1311 and EA NEN 7375:2004 leaching tests were higher than limits set by the U.S. EPA and the Environment Agency of England and Wales related to hazardous waste disposal in landfills. Thus, waste containing chromium should not be allowed to mix with raw materials in the cement manufacturing process. |
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Bibliography: | http://dx.doi.org/10.1016/j.jhazmat.2011.04.077 ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 0304-3894 1873-3336 |
DOI: | 10.1016/j.jhazmat.2011.04.077 |