Bei der Weiterentwicklung nachhaltiger Betonsorten ist CEM II/C-Zement als Alternative zu CEM II/B-Zement eine vielversprechende Variante für die Herstellung von Ortbetondecken. Nachhaltige Betone mit geringerem Klinkeranteil können tendenziell die Frühfestigkeitsentwicklung beeinflussen und dadurch auch die Möglichkeiten, Decken frühzeitig auszuschalen, verändern. Die in dem Beitrag beschriebenen Versuchsszenarien ziehen einen Vergleich zwischen Betonen mit CEM II/C- und CEM II/B-Zement bei verschiedenen Ausschalmethoden.
Early stripping of in-situ concrete floors using sustainable concretes with CEM II/C cements
In the further development of sustainable concrete types, CEM II/C cement is a promising alternative to CEM II/B cement for the production of in-situ concrete floors. Sustainable concretes with a lower clinker content can tend to influence the early strength development and thus also change the possibilities of stripping ceilings at an early stage. The test scenarios described in the contribution draw a comparison between concretes with CEM II/C and CEM II/B cement using different stripping methods. The investigated method of partial stripping of the slab formwork and direct support of the raw concrete slab with floor props without drop head showed a negative effect on the deflection of the slab compared to classic stripping. The measured difference of 1 mm to 2 mm between the three tests is within the fluctuation range of the measurement technology used. In relation to the total deflection of over 70 mm under deliberately borderline environmental conditions and the usual deflections of 20 mm to 30 mm over a 7 m span, these deviations are not considered significant. The tests showed that the optimisation of the concrete composition with regard to CO2 reduction has no restriction on the early stripping of in-situ concrete slabs and is possible in practice depending of course on factors such as temperature and weather conditions. The positive results of the tests with the use of CEM II/C cement in concrete, which led to a reduction in CO2 emissions, are to be confirmed in further studies also at low temperatures and with different compositions.