Influence of chemical-mineralogical properties of limestone on the shrinkage behaviour of cement paste and concrete made of limestone-rich cements

- Drying shrinkage of concretes made of limestone-rich cements is affected by chemical-mineralogical properties of limestone.
- Clay minerals and alkali oxides are dominant parameters for the drying shrinkage of concrete with high limestone contents.
- The contribution of autogenous and carbonation shrinkage to the total shrinkage deformation is almost negligible for cement paste and concrete made of limestone-rich cements.

Shrinkage in concrete structures may lead to cracks which reduce the durability of concrete against aggressive mediums. In prestressed concrete elements shrinkage results in a significant loss of prestressing forces. Limestone-rich cements with limestone contents beyond the values of DIN EN 197-1 were developed in order to reduce the environmental impact of concrete. In this paper, the results of studies on the shrinkage behaviour of cement paste and concrete made of limestone-rich cements up to 70 wt.-% are presented. Results indicated that shrinkage of cement paste and concrete with high limestone contents is strongly dependent on the amount and the chemical-mineralogical properties of limestone. In this context, methylene blue value (MB-value) and alkali oxide content of limestone were identified as the key parameters controlling the drying shrinkage of cement pastes. Depending on the type of limestone, concrete samples made of limestone-rich cements had either higher or lower drying shrinkage than reference samples made of CEM I 52.5 R with the same w/c-ratio. However, lower drying shrinkage deformation was observed in comparison to the reference concrete made of CEM I with a comparable compressive strength. Furthermore, it was ascertained that the contribution of the autogenous shrinkage and carbonation shrinkage to the total shrinkage deformation is almost negligible for cement paste and concrete made of limestone-rich cements.