Suitability of various inorganic substances for use as a minor constituents in cements according to EN 197-1

Cements containing supplementary cementitious materials contribute to the reduction of CO₂ emissions due to their lower content of Portland cement clinker compared to ordinary Portland cements. These lower clinker contents usually result in lower early strengths. Due to their slower strength development the usability of these cements is limited for certain applications.

The (early) strength of cements can be increased by the addition of certain materials. Even though the usage of some of these materials as minor cement constituents might be possible and reasonable from a technical and economical point of view, it is currently excluded acc. EN 197-1. The main scope of this research project was to supply evidence that selected inorganic substances are suitable for the use as minor constituents.

Laboratory cements were tested to investigate changes in (early) strengths due to the usage of the inorganic substances as minor constituents in several cement types. The effects of the different materials on certain standard properties of the cements were analysed in order to disprove negative impacts. The inorganic materials were analysed with respect to their influence on the hydration of the cements and on the microstructure of the hardened cement pastes. Concrete tests were performed to investigate the effects of changes in cement properties on the durability of concrete.

The results are expected to enable cement producers to increase the early strengths of their cements by the selective use of the analysed materials while maintaining consistent cement quality. The use of the analysed materials in cements will initially be possible only via national approvals. In the long term, however, the results can be used as a foundation for the extension of the definition of minor cement constituents in EN 197-1.