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Composite sandwich panels prove to be ideal for building formwork systems. MultiQ Concrete plastics panels made by Quadrant Plastic Composites for Hünnebeck work better and last longer than wooden ones.
(Published on July-August 2008 – JEC Magazine #42)
NICOLA ADAMO, BUSINESS LINE LEADER NON-AUTOMOTIVE, QUADRANT PLASTIC COMPOSITES
At first sight, replacing plywood with high-performance composites may appear to be a prime case of over-engineering. But there is good reason to believe that a new formwork product from German company Hünnebeck, one of the world's top suppliers of formwork and scaffolding, will signal a paradigm shift in the industry..
A new solution
For more than a year, Hünnebeck has been supplying concrete soffit formwork panels made by Quadrant Plastic Composites. The fabrication process involves sandwiching SymaLITE, a very lightweight polypropylene/glass fibre composite, between two skin layers of a high-performance glass reinforced thermoplastic called GMTex™, which is additionally reinforced with various types of fabric. GMTex is reinforced either bidirectionally in the 90° and 45° directions, or only unidirectionally. These products offer a new solution where extreme crash requirements apply.
The MultiQ Concrete soffit and wall panels are direct drop-in replacements for plywood, in 10-to-30-mm thicknesses and fitting together inside standard metal frames. They come away easily from the concrete after it has set to leave a nearperfect surface, and tests indicate that they can be used over 200 times. The panels can be cut and nailed just like wood and are easy to maintain. Humidity does not cause them to swell or rot, and they are highly damage resistant but also easy to repair and recycle.
Composites prevailing over wood
The current trend in the building industry is to replace all-plywood panels with either plastic-coated panels or allcomposite ones. This trend is linked to the need for better quality and longerlasting panels, particularly for rented formworks and formwork used for visible surfaces. Furthermore, the higher prices, lower availability and declining quality of traditional plywood are pushing in favour of a full composite solution. Plywood panels simply covered with plastic skins do represent an improvement over traditional panels impregnated with phenolic resin, but they still have some disadvantages linked to the wooden core and to the different thermal expansion coefficients of the skin and core. Furthermore, the plastic skin plays no role in resisting concrete pressure, and the mechanical performance of a plastic-coated panel is lower because, for the same overall cross thickness, the thickness of plywood is decreased. Humidity can still penetrate the core through nail holes or cuts in the plastic film, causing local swelling that is not acceptable.
An alternative composite solution uses a PP foam core bonded to aluminium skins covered with PP foil. Quadrant Plastic Composites solutions are metal-free, which makes them lighter. They still have better mechanical properties, however, thanks to the very high performance of GMTex skin, and are easier to nail and to recycle.