The use of particle packing models to design ecological concrete

S.A.A.M. Fennis, J.C. Walraven, J.A. den Uijl
Delft University of Technology, Faculty of Civil Engineering and Geosciences, The Netherlands

Ecological concrete can be designed by replacing cement with fillers. With low amounts of cement it becomes increasingly important to control the water demand of concrete mixtures. In this paper a cyclic design method based on particle packing is presented and evaluated on the basis of experiments on cement pastes combined with quartz powder. The packing density of sixteen pastes is measured using the mixing energy test. Furthermore, the cement pastes were tested on compressive strength at 7 and 28 days. Adding quartz powder M600 can increase the packing density by more than 10%. This means that fine quartz powders can improve the packing density to such extent that the cement content can be decreased while simultaneously the water cement ratio is decreased. This occurs for pastes with a packing density higher than the completely saturated packing density of cement. Additional strength tests were performed on two mixtures with constant water cement ratio and showed a 15% strength increase when 20% of the cement was replaced by quartz powder M600. In the design procedure for ecological concrete, increased strength efficiency can be balanced by lowering the amount of cement.

Key words: Cement paste, ecological concrete, filler, particle packing, water demand