Hybrid construction, combining wood with concrete and/or steel, has become a promising opportunity for sustainable architecture.

Innovative and Sustainable Hybrid Structures for the Building Sector

Sika supports sustainable research
Image: The joint project team of Sika Technology, EMPA and ETH Zurich. From left to right: Martin Arnold (EMPA), Urs Burckhardt, Steffen Kelch, Tim Mamie (Sika Technology AG), Prof. Ingo Burgert (ETH/Empa), Sandro Stucki (Empa), Prof. Andrea Frangi, Philippe Gr?nquist (ETH Zürich), missing Stefan V?gtli (Fagus Suisse SA)

On February 20, 2020, a new collaboration was launched between the Swiss Federal Institute of Technology (ETH), Swiss Federal Laboratories for Materials Science and Technology (EMPA), and partner Fagus Suisse SA in the framework on an Innosuisse project. As Sika’s research activities are closely linked to current global trends, such as renewable materials and sustainable constructions, the goal of the collaboration is to conduct research into adhesive bonded timber-concrete composites. ?

Why Explore New Composites?

As traditional materials used in construction are concrete and steel, the building sector is a major environmental polluter. Concrete and steel produce high emissions in their production process, emitting mostly carbon dioxide (CO2) into the atmosphere1 , which accounts for 10% of the world’s annual greenhouse gasses. Therefore, the major goal of the research is to develop new construction materials, which reduce overall CO2 emissions. Wood-concrete composites, especially when combined with beech-wood, could be a sustainable solution as they use the combined abilities of concrete to respond to compressive stress, and wood to tensile stress. Beech-wood is renewable and comes with a low energy consumption in the production process, and, unlike steel and concrete, beech serves as CO2 storage.

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Its high abundance in Swiss forests will increase as a direct consequence of global warming. Hardwoods such as beech and oak are better adapted to future climate requirements (warm winters and dry summers). In order to establish beech as a possible replacement of traditional timber made from softwood such as spruce cooperation partner FAGUS SA will start an innovative production of engineered wood materials out of beechwood2.

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Current drawbacks of wood-concrete floors are the utilization of mechanical steel fasteners to connect the two different materials. Consequently, the competitiveness of wood-concrete composites is reduced, and recycling at the end of the life-cycle is both difficult to realize and costly. ?

Further Development and Market Value

As the first studies focused on encompassing parameters, such as the choice of adhesive and feasibility of the entire ‘wet-in-wet’-process, there is still room for improvement in reducing the amount of concrete and introducing the polymer-based cement developed by Sika, as well as making the entire manufacturing process easier for on-site application.

Wood-concrete hybrids and beech wood CLT have already been realized, namely the House of Natural Resources at the ETH Campus, where wood was used as a finishing material, such as an internal/external surface or structural scaffold. This ‘experimental-house’ is not only a good showcase, but it also set a new way of utilizing the domestic hardwoods for a high-end sustainable building material, positioning the beech-wood composites as a potential gamechanger in the building sector.

1 The Blog of Bill Gates (2/24/2020)

2http://www.nfp70.ch/de/projekte/gebaeude-und-siedlungen/projekt-habert
(2/11/2020)

3 https://honr.ethz.ch/

Concrete wood constructions

A hybrid is something of mixed origin, such as a merging of different materials. Regular steel construction products can be combined with wood materials or inorganic materials to achieve a better performance. The focus is on producing suitable products in the categories:
- Materials, e.g. engineered wood products (EWP).
- Components, e.g. composite floor structures in wood and concrete.
- Systems, e.g. multi-story frames in wood, with stabilizing elements of steel or concrete