The possibilities and limitations of using recycled gypsum (RC gypsum) for cement production will be analysed. The elimination of flue gas desulphurisation gypsum (FGD gypsum) is to be compensated as far as possible by the use of RC gypsum in order to conserve natural resources and reduce the amount of waste going to landfill.
The behaviour of natural calcium sulphates or FGD gypsum in combination with clinker cannot simply be transferred to RC gypsum. Due to a lack of knowledge about the influence of other constituents in RC gypsum on the properties of cement, mortar and concrete, its use is currently very limited, if at all, although this secondary source of sulphate is generally considered to be very suitable. Basic knowledge of the composition of RC gypsum, its behaviour during the grinding process and its solubility in a cementitious environment will be determined. The suitability of RC gypsum for controlling the setting of cement and its influence on strength development and the effectiveness of superplasticisers and air-entraining agents will also be investigated. Requirements for RC gypsum with regard to its use as a sulphate carrier for cement production and any measures required to achieve these will be defined.
SMEs often lack the necessary scientific and technical equipment and personnel to carry out the required analyses. This is therefore a typical IGF task, the results of which will primarily benefit SMEs in the German cement industry. The results can also be used by SMEs in the recycling industry to optimise the processing and quality of RC gypsum. In this way, the competitiveness of SMEs can be maintained and promoted.
