Entity

Time filter

Source Type


Baetzner S.,Forschungsinstitut der Zementindustrie
Cement International | Year: 2010

In accordance with Ordinance (EU) No. 1907/2006 (REACH Ordinance) the content of water-soluble chromium(VI) in cement and cement-containing preparations must not exceed 2 ppm if it is not possible to rule out skin contact during their use. However, excessive chromium(VI) levels were detected in individual cases during the testing of cement-containing preparations although according to the regulations the cement used was chromate-reduced. This initially surprising effect can have various causes. For example, the constituents contained in the preparation in addition to the cement can affect the solution equilibrium of chromium(VI) and/or lower the effectiveness of the chromate reducer. It is also apparent that measured values depend on the test method. This article presents the results of a research project carried out to solve this problem. New findings on the long-term effectiveness of tin(II) sulfate preparations as chromate reducers will be discussed later in a subsequent publication.


Bohm M.,Forschungsinstitut der Zementindustrie
34th International Conference on Cement Microscopy 2012 | Year: 2012

Significant amounts of alternative fuels and raw materials (AFR) are used today in the production process of Portland cement clinker. The use of such materials lowers the consumption of natural resources and reduces emissions of carbon dioxide. However, AFR can lead to changes in the clinker mineralogy and microstructure that can be identified with the help of optical microscopy. Three different principles of how the use of AFR can affect the Portland cement clinker properties are described. The incorporation of raw material and fuel ash particles in the clinker granules and their contribution to the clinker phase formation is dependant on the granularity of the particles, their distribution in the kiln feed and their chemical composition. Like natural raw materials and fossil fuels, coarse SiO2-rich and CaO-rich grains from AFR lead to the formation of belite and free lime clusters, respectively. Laboratory experiments showed that coarse Al2O3-rich particles can also lead to the formation of belite clusters. Due to their combustion properties some alternative fuels and raw materials can locally lead to reducing burning conditions in the clinker bed, which can result in decomposition of alite to belite and free lime. The introduction of phosphorous into the clinker system can partially inhibit the formation of alite via a stabilisation of belite, causing the formation of mixed clusters of belite crystals enriched in phosphate and free lime crystals.


Muller Ch.,Forschungsinstitut der Zementindustrie | Severins K.,Forschungsinstitut der Zementindustrie | Hauer B.,Forschungsinstitut der Zementindustrie
Cement International | Year: 2010

The use of limestone and granulated blastfurnace slag as main constituents in CEM ll/A-LL or CEM ll-S and CEM III cements has had a long and successful tradition in Germany. The combination of the two main constituents in Portland-composite cements has also proved successful. 22 national technical approvals for the use of CEM ll/B-M (S-LL) cements and CEM ll/B-M (V-LL) cements have been issued since summer 2003 in Germany [1,2]. Cements containing fly ash may well become increasingly important. The interesting question nowadays is the performance of cements made with previously unusual combinations or proportions of the cement main constituents, namely Portland cement clinker, granulated blastfurnace slag, fly ash and limestone. This question is directly related to the increasing demands for global climate protection, bearing in mind the sometimes fluctuating availability of the starting materials for cement and concrete. Cements with standard compositions, but also cements with compositions not covered by DIN EN 197-1, were produced as part of the research project entitled "Ecologically and technically optimized cements with several main constituents" [3]. The performance characteristics (e.g. compressive strength, durability) of the concretes produced on the basis of these cements were examined in the laboratory. The work was carried out as part of the "klimazwei (www.klimazwei.de, [4]) - Research for climate protection and protection from climatic effects" programme supported by the Federal Ministry for Education and Research (support code 01LK0502). The results obtained, some of which are reproduced below, cannot be applied to all areas, but they can be used as the basis for further development work.


Muller Ch.,Forschungsinstitut der Zementindustrie | Severins K.,Forschungsinstitut der Zementindustrie | Hauer B.,Forschungsinstitut der Zementindustrie
Cement International | Year: 2010

The use of limestone and granulated blastfurnace slag as main constituents in CEM II/A-LL or CEM M-S and CEM III cements has had a long and successful tradition in Germany. The combination of the two main constituents in Portland-composite cements has also proved successful. 22 national technical approvals for the use of CEM ll/B-M (S-LL) cements and CEM II/B-M (V-LL) cements have been issued since summer 2003 in Germany [1, 2]. Cements containing fly ash may well become increasingly important. The interesting question nowadays is the performance of cements made with previously unusual combinations or proportions of the cement main constituents, namely Portland cement clinker, granulated blastfurnace slag, fly ash and limestone. This question is directly related to the increasing demands for global climate protection, bearing in mind the sometimes fluctuating availability of the starting materials for cement and concrete. Cements with standard compositions, but also cements with compositions not covered by DIN EN 197-1, were produced as part of the research project entitled "Ecologically and technically optimized cements with several main constituents" [3]. The performance characteristics (e.g. compressive strength, durability) of the concretes produced on the basis of these cements were examined in the laboratory. The work was carried out as part of the "klimazwei (www.klimazwei.de, [4]) - Research for climate protection and protection from climatic effects" programme supported by the Federal Ministry for Education and Research (support code 01LK0502). The results obtained, some of which are reproduced below, cannot be applied to all areas, but they can be used as the basis for further development work.

Discover hidden collaborations