Quality Assessment

Research project

“SpeedTeCC”

Economical production of high-quality wood-concrete composite elements via application of an innovative rapid-bonding technique and the use of hardwood

In cooperation with the Institute of Joining and Welding Techniques (TU Braunschweig) and the department for Timber Structures and Building Rehabilitation (University of Kassel), we are developing procedures and technologies for the quick and simple production of high-quality wood-concrete composite elements through application of an innovative rapid-bonding technique. This new type of joining technology is intended to improve the structural properties, the economic viability and the re-usability of wood-concrete composite elements and therefore contribute towards the increased use of renewable raw materials in solid construction. We thereby take particularly into account the use of hardwood as a regionally available raw material source.

© Gregor Wisner | TU Braunschweig
Bonded wood-concrete composite (bonding with a conductively heated hotmelt adhesive tape); Test specimen for compression-shear testing

In wood-concrete composite constructions (WCC constructions), the specific compressive and tensile strengths of concrete and wood are combined in a superb manner, e.g. as ceiling components. Furthermore, WCC elements exhibit not only improved properties as regards acoustic insulation and structural fire protection but also an increased load-bearing capacity with a low component height. In addition to its load-bearing function, the concrete also undertakes the construction-related protection of the wood and acts as a storage mass in connection with the building climate control. The use of wood strengthens moreover the growing desire for the application of renewable raw materials in the construction sector, which can also often be easily obtained locally.

Until now, the bonding of WCC elements has been primarily carried out through mechanical connection means (e.g. screws) or via a mechanical fitting (comb-like interlocking of directly wet-cast concrete in grooves of the wood construction). In addition to high costs for the necessary assembly work, the occurrence of moisture in adjacent components and the shrinkage of the concrete - which can even lead to tension and slippage in the area of the grooves - can be listed as possible disadvantages.

Bonded WCC elements for high-rise buildings represent an efficient and, in many respects, optimized construction component and would be a completely new product group. Amongst other things, this method of bonding enables a rigid bond, in contrast to mechanical joining. In addition, the application of the conductive rapid-bonding technique using special adhesive tapes, which is pursued in this research project, enables a fast, operationally simple and secure construction technique for on-site assembly. Re-usability following the end of the useful life of individual components and elements presents a further advantage; this can be graded as more valuable than the simple material recycling carried out until now with the down-cycling of concrete to concrete granules and the thermal utilization of wood.

This innovative joining technology can be applied across all sectors (wooden construction/solid construction) and is intended to benefit the construction sector - which is strongly characterized by medium-sized companies - in the relevant branches of wooden construction as well as the prefabricated reinforced concrete industry, adhesive manufacturers and installation companies. 

The assessment bases developed within the research project and the testing methodology will be introduced into the discussion on the further development of normative rules at European level. As no comparable scientific studies are currently known, it can be assumed that the further development of normative rules for testing methodology and the provision of normative rules for the design and dimensioning of bonded WCC components will be significantly shaped by the research project.

Results

We discovered that not only two-component epoxies (2C-EP) but also heat-curing single-component polyurethanes (1C-PU) are suitable for bonding on smooth concrete surfaces. Smooth concrete surfaces can be bonded with spruce and beech wood if release agents are stringently avoided during the concrete production process. Through this procedure, the production of TCC elements becomes simpler and therefore economically more attractive.

Project partners

  • Technische Universität Braunschweig, Institute of Joining and Welding Techniques (ifs)
  • University of Kassel, Timber Structures and Building Rehabilitation (FHB)

Funding

Funds: 
IGF Research Project No. 19417 N is supported by the AiF e. V. within the framework of the program for the promotion of industrial joint research (IGF) from the German Federal Ministry of Economic Affairs and Energy (BMWi) on the basis of a decision by the German parliament.

The project is supervised by the International Association for Technical Issues related to Wood (iVTH), together with the German Welding Society (DVS), as research associations.

 

Project duration: 
1.4.2017 to 30.9.2019