A team from TU Graz has developed a prefabricated brick wall that can be dismantled and re-used without being destroyed. This reduces emissions significantly and conserves valuable resources.
The construction sector still has some way to go in terms of reducing the consumption of resources and greenhouse gas emissions. One of these relates to the construction waste produced during the demolition of buildings. Buildings used for rather short periods of between ten and 20 years, such as consumer markets, have a negative impact on the balance sheet. In the Re-Use Ziegelwand project, a team from Graz University of Technology (TU Graz), together with the biggest Austrian brick producer wienerberger, has now developed a solution that decouples the service life of the building materials from that of the building. The centrepiece is industrially prefabricated brick wall elements that are not joined by conventional mortar joints but by using reversible joint solutions. This means they can be re-used several times after a building has been dismantled.
60 per cent CO2 savings over three life cycles
“Bricks are very high-quality building materials and their production is very resource-intensive. It therefore offers enormous advantages if they can be removed non-destructively after a building has been used, and re-used elsewhere,” says project manager Hans Hafellner from the Institute of Building Physics, Services and Construction at TU Graz. “The results of our research to date show that a significant proportion of total emissions can be avoided during the second phase of use through reuse by developing an innovative jointing solution. Considering three life cycles, CO₂ emissions can be reduced by around 60 per cent compared to conventional construction methods.”
A particular challenge in the realisation of the reusable brick walls was to ensure that they could be dismantled and at the same time meet all structural requirements in terms of tolerances, statics, tightness, thermal insulation and stability. In addition to the non-permanent joint solution, the team therefore relied on a few other necessary elements. The brick thickness of the walls is 44 cm and the bricks contain insulating wool to guarantee sufficient thermal insulation. The prefabricated brick walls are also pre-plastered at the factory, which reduces the work involved on the construction site. There are two options when it comes to statics and stability. Either the roof of the building is heavy enough to stabilise the structure or threaded rods which run through the bricks vertically and are pre-stressed provide the necessary stability.
Successful dismantling and reconstruction
The team tested its developments using a demonstrator building. Not only did the joints and wall structures fulfil all the requirements, but the building was still fully functional even after being dismantled and rebuilt at a different location. To ensure that this also applies to buildings after ten to 20 years of use, the researchers rely on what is known as modal analysis. A body, in this case the pre-built brick walls of the building, is stimulated by means of vibrations in order to first determine the natural frequency in a healthy state. If there is a change in the natural frequency at some point during the period of use, it is possible to determine the load-bearing capacity of the walls without having to use destructive test measures.
“The successful construction, dismantling and reassembly of the demonstrator on a large scale confirms the technical feasibility and robustness of the system under realistic conditions,” says Andreas Trummer, who supervised the project at the Institute of Structural Design at TU Graz. “Ultimately, this solution not only benefits the users of the building, as it has a higher residual value at the end of its service life, but also the environment.” In addition to the Institute of Building Physics, Services and Construction and the Institute of Structural Design as well as wienerberger, the Laboratory for Structural Engineering at TU Graz was also involved in the research. The project was funded by the Austrian Research Promotion Agency FFG.