Wide ceilings without steel
Fast and dry ceiling construction with steel-free wood-concrete composite construction ‘maxit DUOBLOCK’
The construction of large-span ceilings was until now considered impossible without structural steel. With the new ‘DUOBLOCK’ composite solution, an ecological, steel-free alternative is now coming onto the market that can change ceiling construction in the long term. Solid wood and concrete are combined here in a hybrid construction and enable ceilings over eleven metres wide for all common building types. A specially developed grouted concrete creates a force-fit connection with the solid timber beams. In addition to its strengths in terms of statics, sound insulation and fire protection, ‘DUOBLOCK’ is particularly impressive from an ecological point of view with around 64 per cent less CO2 emissions compared to conventional constructions.
It is no secret among experts that the use of structural steel has an above-average negative impact on the energy balance of a building. However, environmentally conscious planners and building owners now have a sustainable alternative at their disposal: the steel-free wood-concrete composite ceiling ‘maxit DUOBLOCK’ (DIBt approval, Z-9.1-904). This is a ceiling construction made of solid wood prefabricated parts to which a special concrete casting compound (building material class A1) is applied on site in thicknesses of 50 to 80 millimetres. This can be used both as an exposed and clad ceiling and is ideal for ecological timber and solid construction.
The new wood-concrete hybrid solution is regarded as a milestone towards a more environmentally friendly construction industry. Almost ten years of intensive joint research and development work with the company Brunthaler Holzbau (Egglham) and the Institut für Holzbau (IfH, Augsburg) preceded the market launch.
Wood and concrete in harmony
Never before have opposing materials such as wood and concrete been combined in a building product in such a balanced way. Thanks to a special grading curve and high water retention capacity, the concrete casting compound developed by maxit forms a force-fit connection with the solid timber beams - using special milling and dowels made from beech wood. While the beams absorb the tensile forces of the bending stress, the concrete bears the compressive load. In this way, the strengths of both composite materials can be fully exploited and large spans of over 12 metres can be achieved - with 50 percent less weight per unit area compared to standard reinforced concrete ceilings. The undersides of the ceilings can be finished in different visible qualities or clad.
With around 64 per cent less CO2 emissions, ‘DUOBLOCK’ has a clear sustainability bonus. The global warming potential is reduced by 20 kg CO2e/m2 and the primary energy requirement by 40 per cent. This is made possible by using 40 per cent less concrete and completely dispensing with reinforcing steel. This is also an important economic advantage over reinforced concrete ceilings, whose energy and manufacturing costs have risen noticeably due to the current steel and cement prices.
Rapid construction process guaranteed
Alternative wood-concrete ceiling systems have also been dependent on concrete anchoring and steel construction mesh until now. In addition to the ecological disadvantages, however, installation in particular proves to be enormously time-consuming, as reinforcement and grouting can only be carried out floor by floor, thus significantly slowing down construction progress. In contrast, builders using ‘DUOBLOCK’ benefit from a fast and dry construction process, as the next storey can be added immediately after the slab has been laid. The concrete is only poured once the building has been erected and is protected from the weather. To ensure rapid processing, the concrete is delivered to the construction site in a silo ready for use, with the flowing screed process enabling a high area output. Stripping times are limited to three to ten days after casting. The minimal concrete cross-section ensures low exposure to moisture. Even faster results are possible with industrial prefabrication.
And maxit does not see itself at the end of the development process: in the medium term, the cement-bound concrete is to be replaced by a purely mineral anhydrite flowing screed. As a non-thermally treated natural product that is merely finely mixed, anhydrite has a lower primary energy requirement. Long-term scientific tests have already produced promising results.
Technical data and processing instructions as well as further information on the new, steel-free wood-concrete composite floor ‘DUOBLOCK’ are available at www.maxit-duoblock.de (only in German).