At the end of 2021, Peikko Group Corporation, the global forerunner in Slim Floor Structures, Wind Energy Applications and Connection Technology for Precast and Cast-in-situ, implemented a pilot project in which a load-bearing frame of concrete elements and slim-floor beams was assembled, disassembled and reassembled. Precast manufacturer, Consolis Parma and Finnish training and research organization, TTS were also involved in the project which was carried out in Vantaa, Finland. The main purpose of the project was to prove that the connection technology between load-bearing structures unlocks the reuse potential of precast concrete elements.
In 2022, the construction of a residential building consisting of demountable connections and a reusable load-bearing frame was started. It is the first residential building in Finland where the principles of Designfor- Disassembly have been applied, to allow direct reuse of its building components. Connections between load-bearing structures were designed by adopting the best practices from the pilot project in 2021.
These efforts are in line with the European Commission’s Circular Economy action plan, which defines concrete ways to achieve the EUwide targets to become carbon neutral by 2050. Given that the construction sector produces over 35% of all EU territory waste, 5-12% of the world’s greenhouse gas emissions, and used up 29% of all non-renewable raw materials in 2018, there is huge pressure on the construction industry to find more sustainable ways of operation.
One aspect of sustainability and circular economy is to keep products, components, and materials at their highest utility and maintain their value throughout the entire life cycle of a building. Connections may be designed to enable an effective dismount of building components as well as support the modularity of the building. The potential of existing building stock may also be utilised if their structures are found to meet modern requirements. These methods could effectively reduce the need for new structures and buildings, thus reducing both CO2 emissions and the consumption of raw materials.
PILOTING THE FUTURE
While the demountability and reusability of steel structures has been studied and is easier to put into practice, concrete structures require installation tolerances on site and grout makes disassembling difficult. There have thus been few attempts to reuse concrete structures in practice.
In order to produce novel information and break down negative prejudices haunting over the reusability of precast concrete elements, Peikko implemented a pilot project where dismount and reuse of such structures were tested in practice. The test was done by assembling a frame consisting of 320mm deep DELTABEAM® Green composite beams, which was made from steel having 90% or higher recycled content, and ‘green’ hollow core slabs and precast columns, which are 50% lower in CO2 emissions than standard slabs due to PARMA Green™ technology. None of the components were damaged in the dismounting process.
During the reassembly, all disassembled components were placed in their original position and the bolted connections were reconnected (figure 8). It can be concluded that the current connection technology already enables the dismount and reuse of concrete elements. However, does the dismount of structures achieve economic viability, or does reusability have a clear effect on reducing environmental load?
LESS ENVIRONMENTAL LOAD WITH SMALLER COSTS
After the pilot project, the environmental and economic impact of dismount and reuse were studied by running a comparison between two scenarios:
1) Reassembly of the frame by using the same dismounted components
2) Reassembly of the frame by using brand new building components
For the latter case, a similar precast concrete frame was assumed, but without the connection technology supporting the dismount. In that case, the reassembly of the frame simply meant the delivery of completely new components. Economic effects were estimated by calculating the costs associated with materials and processes (€) while environmental effects were determined as CO2 emissions (kgCO2). The study and its results are discussed more deeply in the White paper Dismount and reuse of precast concrete frame.
It was concluded that, although considering dismount and reuse in the design (scenario 1) produces additional costs and CO2 emissions in both the first assembly phase and disassembly phase, economic savings and environmental benefits are significant in reassembly phase when compared to manufacturing and transporting entirely new building components (scenario 2). In the pilot frame, which was implemented under the pilot project, disassembly and reusability resulted in approximately 35% cost savings and 50% lower emissions.
FROM PILOT TO PRACTICE
While the pilot has proven the technical feasibility of the current connection technology, the study for economic and environmental gains has revealed the leashed potential of dismount and reuse of concrete structures. One of the key challenges for applying design-for-disassembly as common practice is lack of regulative norms, which would provide rules and boundaries for designers. International standard ISO 20887 is one the few to present principles and requirements related the topic, and the concept of bolted connections is well in line with the standard. However, larger scale of standardisation work is further required. To fuel the ambition, more and more references are needed to reveal the best practices for dismount and reuse.
The residential building which has been constructed in Finland with demountable and resusable load-bearing structures, as the first of its kind, is a concrete benchmark for the buildings in the future, which are asked to be circular without compromising the appealing appearance and the structural performance.
KEEPING OUR EYES ON THE FUTURE
The future holds much innovation ahead, and Peikko is proud to be part of the solution, as the company continues to operate in line with its vision to offer a faster, safer, and more sustainable way to design and build
