Latest cement chemistry findings

Over 130 participants gathered for the “Cement Chemistry” conference at the VDZ (German Cement Works Association) in Düsseldorf on 01.04.2009 to exchange ideas on current ­
cement chemistry problems. After a speech of welcome and an introduction by Dr. M. Schneider, General Manager of the VDZ, Dr. H.-M. Ludwig gave a report on the activities of
the Cement Chemistry Technical Committee in recent
years. The committee been involved in the following research activities:

– Influence of the burning and cooling conditions on the properties of Portland cement clinker when using secondary fuels

– Improvement of the early strength of blastfurnace cements by reactive aluminium compounds

– Influence of the reactivity and quality of granulated ­blastfurnace slag on the sulfate resistance of concretes and mortars containing granulated blastfurnace slag

– Influence of concrete admixtures on the leaching behaviour of trace elements

– Influence of fly ash on the composition of the pore solution

– Reaction of alkali-sensitive aggregates

– Effect of the alkali reactivity of test sands on the evaluation of potentially alkali-reactive aggregates

– Chromate reduction in preparations containing cement

Dr. Ludwig also reported on the activities of the various working groups that are associated with the technical committee.

Prof. Dr. A. Wolter then gave a lecture on new strategies for binders. He differentiated between various binders and production methods and, for example, explained the design basis for CEM X and M³K multimodal multicomposite cements.
He also discussed belite cements, eco cements, sulfoaluminate cements, magnesia binders, celite cements and glass cements and explained their possible applications.

Dr H. Möller spoke on the production and application of cements containing fly ash. He pointed out that the cement industry should be prepared for increased use of fly ash, but that its application required technological expertise. Secondary grinding of the coarse fractions in fly ash improves its effectiveness compared with plain mixing.

In his lecture entitled “Building for eternity? The durability of concrete structures” Prof. Dr. C. Gehlen described how demand profiles in the construction industry might look in the future. By analogy with the life cycle of human beings he pointed out that the consideration of sustainability should not just include single stages, such as the production, of a building material – the entire application must be taken into account.

Following this Dr K. Lipus described the many advantages offered by the use of scanning electron microscopy in the cement industry (Figs. 1 and 2). It can be used from the assessment of clinker and investigations into cement hydration to the analysis of damage in mortars and concretes. With modern methods, such as cryo-SEM, it is possible to obtain information about the individual stages of the hydration of cement.

Dr. W. Cordes gave a report on the properties and use of bypass dust in the cement industry. Any further increase in the percentage of secondary fuel with the same level of processing for chlorine will lead to greater quantities of bypass dust. However, its use in cement and other building products is restricted, so there is increasing interest in alternative ways of using it. 

Dr G. Schnedl then contributed a report on the subject of secondary fuels. His conclusion was that it is possible to control the use of a high proportion of secondary fuels. From the quality point of view it is best to use them in the calciner. However, it is essential that they have a suitable analysis. The aim is to recognize the different influencing variables and the limits of secondary fuel usage. However, the expenditure on quality assurance is certainly a significant cost factor.

Ms M. Engel then spoke on the subject of “Modern fuel analysis – overview and selected examples”. This dealt with a wide and often very involved area of operation in which it is necessary to maintain existing standards from the sampling and analysis to the evaluation and interpretation. The sampling and preparation stages are particularly important for establishing reliable and informative analysis results.

The final lecture by Dr M. Paul was devoted to the subject of “Inline/online analysis”. He described the methods of analysis that are available in the different process stages. Using the example of the analysis of raw materials he showed that the choice of the most suitable method is an important aspect. For example, XRF analysis can in fact provide more accurate individual results than PGNAA but the latter method characterizes the entire stream of material without any time delay or processing.

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