Calcium sulfate composite binders containing pozzolans for use in planar products
![2 Time taken to reach the maximum change in length of the mixes [in days]](/uploads/images/2018/w300_h200_x600_y321_2-c1154f8dd205401d.jpeg)
![3 Interaction between the pozzolan/cement ratio and the proportion of hemihydrate plaster on the time taken to reach the maximum change in length of the mixes [in days]](/uploads/images/2018/w300_h200_x600_y323_3-fdb449e7502c13fc.jpeg)
![4 Maximum values of the changes in length [mm/m]](/uploads/images/2018/w300_h200_x600_y310_4-9ea723de35f5fb5f.jpeg)
![7 Drop in strength [%] due to moisture in a comparison of dry and wet strengths after 7 days](/uploads/images/2018/w300_h200_x600_y340_7-610543bdc9b4ed72.jpeg)
The aim is to produce planar products based on calcium sulfate composite binders. In initial trials it was demonstrated that (up to five-times) higher strengths can be achieved with this mixed binder than with pure hemihydrate plaster mixes for the same water/binder ratio. The strength losses caused by moisture that are typical of calcium sulfate can, depending on the mix formulation, be significantly reduced so that they can be lowered to the same level as cementitious systems. The timing of expansions caused by ettringite can be controlled by suitable mix formulations so that they are completed within 7 days at the latest.
1 Motivation
The results described here were obtained during a ZIM research project with the partners Lindner AG, GiB Gesellschaft für innovative Bautechnologie mbH and the F.A. Finger Institute for Building Material Engineering at Bauhaus-Universität Weimar. This partnership is developing fibreboard based on special, energy-efficient, calcium sulfate composite binders.
This binder system consists of calcium sulfate binders that are capable of setting and have a low primary energy requirement with properties that can be sustainably improved by carefully controlled combinations with cement and...
