Dr Jörg Rickert
Compared to Portland cement, the water demand of cements with calcined clay may be higher. Thus, concrete produced using these cements with calcined clay may be stiffer and may require a superplasticizer. However, knowledge on influences of these cements on the workability of concrete and their interactions with superplasticizers was available to a relatively small extent only.
The aim of the research project was to determine interactions between superplasticizers and cements with calcined clay. It was determined how the proportion of calcined clay in the cement as well as the dosage of superplasticizer influences the rheological properties of fresh cement paste and concrete. In the foreground were influences of the calcining conditions of the clays on the workability of cements with calcined clay and on the effect of different superplasticizers as well as influences of the test temperatures (“summer”, “winter”).
The results of the project give important information to cement producers to enhance the workability of cements with calcined clay. Concrete technologists receive important information to choose the right superplasticizer for the particular concrete composition and the actual time of the year. Both factors contribute to prevent undesired reactions in concrete.