Blog posts - Recreate

October 18, 2024

Arnaldur Bragi Jakobsson

Second Wind explores the potential of reusing pre-cast concrete elements from an obsolete apartment building in Helsingborg, Skåne County, Sweden.

As part of the ReCreate initiative, which encourages the sustainable repurposing of concrete components, I collaborated with Helsingborgshem, the city’s municipal housing company, to develop a new rowhouse typology of approximately 100 m², alongside a two-story multifamily apartment building on the same plot.
The project aimed to minimize modifications to the existing structural components, preserving their original form as much as possible while adapting them to new uses. The rowhouses, arranged in an L-shape with a southwest-facing courtyard, serve as rental units and highlight the potential of reused materials in creating modern, functional spaces. The apartment buildings, located on the north and south sides of the site, further demonstrate the versatility of these repurposed elements.

Throughout this process, I sought to maintain a connection to the original architectural context of the Drottninghög area, respecting its mid-20th-century character while introducing new, sustainable housing solutions. This project illustrates the significant environmental benefits and creative opportunities in reusing existing building materials, paving the way for more sustainable construction practices.

Rowhouse plan (Arnaldur Bragi Jakobsson)

by ReCreate project

September 27, 2024

Written by Linnea Harala & Lauri Alkki

The ReCreate pilot projects in Finland, Sweden, Germany and the Netherlands highlight diverse approaches to implementing concrete element reuse, each influenced by unique building types, contexts and organizational structures. An initial analysis by ReCreate’s business research work package (WP7) has revealed distinct patterns in these approaches, primarily categorized into centralized and decentralized models. During the ReCreate annual meeting in Zagreb, WP7 also organized a workshop to present the identified approaches to other project partners and to get feedback on the initial analysis.

Figure 1 & 2. Workshop between ReCreate partners at the annual meeting in Zagreb on the preliminary results of the two different approaches.

The identified approaches – A) centralized & B) decentralized

The centralized approach is characterized by a single key actor managing multiple phases of deconstruction and reuse. This model is most prominent in the Netherlands. There, the same actor is responsible for deconstructing a building and reusing most of its elements in a new structure, a process referred to as 1-on-1 reuse. The ecosystem in a centralized model is simple, with a central hub managing all operations. The key actor controls the flow of information and data mostly internally, ensuring streamlined communication and decision-making. In addition, the key actor’s business model extends to both deconstruction and reuse, highlighting its capabilities and resources. A strong single actor can oversee the entire project, facilitating optimized and controlled execution. With one key actor at the helm, there is a clearer distribution of tasks and responsibilities. On the other hand, success depends heavily on the performance and capabilities of the key actor.

Conversely, the decentralized approach involves multiple specialized actors managing different phases of deconstruction and reuse. This model is evident in Finland and Sweden, where elements are harvested and reused in various buildings. The ecosystem in the decentralized approach consists of several specialized, complementary companies and organizations. Therefore, effective communication and data sharing between these actors has been identified as a critical factor for success. In the decentralized approach, each actor operates based on its expertise and specialization, contributing to a more diversified and flexible business landscape. The feasibility of the decentralized model depends on how well the project organization coordinates multiple companies. This complexity requires robust inter-organizational collaboration to ensure smooth transitions between phases, as multiple actors require more discussion to define responsibilities at different stages, at least initially.

Overall, it can be seen that in the centralized approach, the control of the dominant key actor can streamline operations, but it relies heavily on this actor’s capabilities. On the other hand, the decentralized approach, while more complex, offers flexibility and the potential to leverage a wider range of expertise. In both approaches, the work phases and tasks are largely the same, but their overlap and sequence may vary. Ultimately, understanding these approaches allows for better strategic decisions throughout the concrete element reuse process, promoting more sustainable and efficient construction practices.

by ReCreate project

August 30, 2024

Lina Brülls, Graduate Architect and Master’s Student in the Computer Science Program at Chalmers University of Technology

The master’s thesis “Resource-Driven Design” explores how the design process can be adapted to facilitate the reuse of structural concrete elements. Research done in the thesis indicates that current design and data processes are not easily translatable to reuse scenarios, where preexisting structural and geometrical attributes of materials must be considered. Based on this, three key research questions are formulated: identifying the necessary data for the reuse design process, developing a Grasshopper Rhino plugin for data integration, and applying this tool in case projects with the aim of optimising reuse.

The developed Grasshopper plugin, programmed in C#, enables data handling from Excel into Rhino. It generates structural modules from reused hollow-core and load-bearing wall elements based on desired design parameters. The tool was tested in three architectural projects on Siriusgatan in Bergsjön. Regular consultations with the ReCreate team at KTH provided helpful expertise and feedback throughout the development process.

The study’s findings suggest that integrating data early in the design process can improve the efficiency and feasibility of reusing structural elements. One key challenge encountered in this project was planning within the constraints of the generated load-bearing modules. Including glulam beams introduced necessary flexibility, enabling adjustments in level height and allowing the removal of some load-bearing wall elements.

by ReCreate project

August 9, 2024

Tommi Halonen, project manager, City of Tampere, Finland

Sometimes I get asked: ‘Why is the City of Tampere participating in ReCreate, and what is our role in the project?’ It might be much easier to see why a university or a construction company is taking a part in a project where the goal is to (de)construct buildings in a novel way. But what is the city doing in ReCreate, especially when the deconstruction pilot was not a public building? From my viewpoint, cities have in particular the following two roles to play in the circular transformation:

Role 1: developing public processes that enable the implementation of CE solutions.

First, cities have a significant role as regulators in the construction industry. If there are any issues related to public regulation that do not allow reuse or make it extremely bureaucratic, it is impossible or very difficult (or expensive) to create business out of ReCreate or any other circular solution. There are especially two matters that are regulated by the city authorities that are worth paying attention to: (1) implications of waste legislation and (2) product approval practices.

(1) During the ReCreate project, we’ve had multi-stakeholder discourse in Finland about whether reused building parts should be considered as waste or not – some stakeholders opposed, and some supported the waste status. However, at the end, it is the city officers that control the matter and they needed to decide how to proceed with it. I cannot go through all the matters the authorities needed to consider in order to clarify the issue but in brief, the hardest part was to find a balance between environmental protection and excessive (too heavy) bureaucracy. Eventually the authorities were able to clarify their policies so that, in Finland, reused components are not considered as waste when certain pre-requisites are fulfilled. At the time of writing this blog, we’ve also received an official decision that ReCreate elements are not considered as waste. This is a huge development step in the Finnish industry towards circularity.

(2) Another matter the cities regulate is the product approval of reused building components. Unlike new products, the CE (conformité européenne) mark does not apply to reused products. In Finland, the products are approved as part of a so called ‘building site approval process’ that is regulated by the municipal building supervisors. There is no prior experience of the approval process. Consequently, the situation is now very similar to the aforementioned case: city authorities must again develop practices and policies that ensure that essential technical requirements are met when reusing components but are not too burdensome for practitioners to comply with. As I write this blog, we are in the process of discussing these practices with the authorities.

Role 2: creating needed incentives for companies for CE development.

Cities are not only passively enabling the circular transformation, but they can – and they must – actively initiate the change, too. Indeed, me and my colleagues have received feedback from multiple companies stating that due to early stage of the circular development, the industry cannot move to circularity solely with the help of market drivers and market logic. The companies emphasized the need for public initiatives that create incentives for circular development. Cities have at their disposal policy instrument that can create this market push. The most notable instruments are (1) public procurements and (2) plot handovers.

(1) During the project, we have had multiple meetings and workshops with the leaders of the city so that Tampere could incorporate reuse to future procurements and building projects. Sooner or later, reuse of building components will break through to public procurements and when it does, it will have a significant impact on the market.

(2) Another policy instrument that can initiate change is the plot handover process. In Finland, municipalities are the biggest landowners in urban areas. Traditionally, sustainability or circularity goals have not been part of the handover processes. However, in 2022 the City of Tampere initiated an all-time first circular plot competition. It was a success with nearly 20 building proposals and applications and received a lot of positive attention in general as well as in professional media. Many cities got inspired and wanted to repeat the circular competition. What we decided to do with my colleagues was to launch a working group, the goal of which was to create upgraded and unified circular criteria for the municipalities. Around 30 experts worked on the criteria for a year, and after receiving feedback in different workshops and seminars, we were able publicize the criteria at the beginning of this year. Now, we are keen to see the impact that the criteria will create when the cities are starting to include them to their plot handovers and competitions.

All in all, while this blog is not an exhaustive list of all the role the cities have in the circular transformation, I do hope that I was able make the case that cities are one of the major players enabling the transition. Indeed, for me personally, it is very difficult to see how the industry could make the transition to the circular economy on a large scale if the cities are not developing public policies and processes to promote circularity.

by ReCreate project

August 2, 2024

Lagemaat at TU/e (in collaboration with the Dutch cluster)

As part of the international @ReCreate project, we are working closely with various partners, including the Dutch cluster. This month, the Eindhoven University of Technology (TU/e) will conduct further research at our site to test concrete elements from the Prinsenhof pilot project. This research helps us understand the impact of weather conditions on the stored elements in Heerde. The materials from the Prinsenhof project will thus find a new purpose at the Circular Center in Heerde.

An important aspect of our collaboration with TU/e is testing various concrete elements for their reusability, enabling their circular application. In a recent vlog, Marcel Vullings (TNO) and Fred Mudge (TU/e student) share their findings from these tests. They investigate how concrete parts can be dismantled and what new applications are possible in future projects.

These tests are crucial for the progress towards a circular construction sector. By reusing concrete elements, we save on new raw materials and reduce tons of CO2 emissions. The collected data forms the basis for future projects.

Examples of projects that strongly focus on material reuse include the Zuiderstrandtheater in Scheveningen and the Ruijgoordweg 80 project in Amsterdam. Through this approach, we continue to innovate and contribute to a sustainable construction industry.

by ReCreate project

July 5, 2024

Project and industry partners involved:

BTU Cottbus-Senftenberg: Prof. Dr. Angelika Mettke, Viktoria Arnold, Jakob Fischer, Christoph Henschel,
Sevgi Yanilmaz, Anton Leo Götz

IB Jähne: Peter Jähne, Milena Zollner

ECOSOIL OST: Dietmar Gottschling, Bernd Mathen, Jens Muschik, u.a.

Figure 1 – 3D Model of the test building (Source: BTU)

The objective for the test construction was to generate findings on the practicability of the construction method by reusing precast-reinforced concrete elements. The reassembly and disassembly of the test building was carried out by and in cooperation with the German ReCreate industry partner ECOSOIL. In particular, the combination of used reinforced concrete elements with timber stud walls was to be tested, as well as the new steel connectors developed as part of WP5. A new filling mortar was tested for its applicability to form the butt joints between the precast concrete elements.

Figure 2 – Donor Building Type WBS70-C before deconstruction (Source: BTU)

The donor building for the test building was a five-story WBS 70-C apartment block on Karl-Marx-Straße in the small town of Großräschen in Brandenburg. A partial demolition was carried out here as part of a refurbishment project, in which the upper 2 or 3 stories were deconstructed. From the deconstruction mass, 12 precast concrete elements were transferred to Cottbus for the test building: 3 exterior wall panels, 6 interior wall panels and 3 ceiling panels (see Fig. 3) after they had been selected and marked in the installed state.
The element-oriented deconstruction began in November 2023 and was completed at the end of February 2024. The dismantled precast reinforced concrete elements were stored on the construction site in Großräschen for another month before being transported the approx. 40 km to Cottbus in April 2024.

Figure 3 – Overview of elements needed for the test building (Source: BTU)

Figure 4 – Floor plan of the test building (Source: BTU)

When designing the test set-up, an attempt was made to reproduce as many different element connection situations as possible. These include corner connections between two concrete elements or between a concrete element and a timber stud wall (corner connector), longitudinal connections between two concrete elements (longitudinal connector) or the centred connection of a concrete wall element with a concrete element installed at right angles (T-connector) – see Fig. 5 and 6.

The newly developed connectors are made of 8 mm thick flat steel and are attached to the top of the wall elements with concrete screws. The connectors can be fixed in both concrete and wood and are therefore very suitable for combining these two building materials. The steel connectors mounted on the top can be embedded in the mortar bed required for the ceiling elements anyway, so that they do not present any structural obstacle and are also protected against the effects of fire and corrosion.

Figure 5 – 3D Models of the newly developed connectors (Source: BTU)

Figure 6 – Placement of the steel connectors in the test building (Source: BTU)

In addition, the design concept of the test building was planned in such a way that a wall element and a ceiling element were to be cut to size in order to test the effort involved in sawing the concrete and whether the cut precast concrete elements could be used as intended.

The former airfield in Cottbus, which had been decommissioned for several years, was chosen as the location for the test building. There was sufficient space, a load-bearing concrete slab as a base and a suitable access road for the delivery of the reinforced concrete elements.

In March 2024, work began on the production of the timber stud walls and the setting of the masonry calibrating layer to prepare the construction site for the installation of the concrete elements. The used concrete elements were delivered to the construction site on April 18 and 19 and stored in the immediate vicinity of the test building. They were professionally reassembled within two days. Each wall element was placed on the calibrating layer (see Fig. 7, center), leveled and secured using mounting braces (see Fig. 7). The elements were joined together using the above-mentioned flat steel connectors. The use of the innovative SysCompound joint mortar (based on fly ash and recycled aggregate) was tested for the butt joints between the concrete elements. Various formulations for the SysCompound were developed and tested in the laboratory in advance. The bond between the old concrete and the fresh joint mortar was of particular interest. In this respect, not only the mortar strength played a role, but also the shrinkage behavior of SysCompound in comparison to commercially available joint mortar mixtures.

Figure 7 – construction process of the test building (Source: BTU)

Figure 8 – construction process of the test building (Source: BTU)

The assembly of the test construction went smoothly and quickly (see Fig. 8) so a positive conclusion can be drawn for future pilot projects. The flat steel connectors have proven successful due to their simple fastening by means of screws (assembly) and disassembly; the combination of reinforced concrete and timber stud wall elements has proven to be practicable and the sawn concrete elements could be reassembled without any problems.
From a planning point of view, it is recommended that larger dimensional tolerances of the concrete elements be taken into account, as the actual geometric dimensions sometimes deviate from the planning and the edge zones of the dismantled concrete elements are no longer level in some cases. Concrete sawing work is known to be feasible but should be reduced to a minimum due to the high costs and energy required. When filling the joints, it turned out that due to unevenness or broken edges and corners of the concrete elements – as explained above – significantly more grout was required in some cases than assumed in the planning.

Figure 9 – Aerial view of the test building after completion (Source: C. Busse + S. Karas)

Overall, the test construction on the former airfield site in Cottbus was a complete success. The BTU team would like to take this opportunity to thank the landlord DLR for the space used, the skilled workers from ECOSOIL and the logistics service provider Auto Klug. Without the cooperation of the aforementioned parties, the realization of the construction project in this form would not have been possible. In mid-May 2024, the test building was dismantled/disassembled again and transported away for temporary storage at a recycling yard 42 km away. If the used concrete elements are not requested as components for reuse, they will be recycled and are therefore still available through material recycling.

by ReCreate project

June 20, 2024

Antti Lantta, project manager (building demolition), Umacon & Juha Rämö, technology director, Consolis Parma

The earth’s carrying capacity is being tested, and it cannot sustain the growing use of virgin natural resources on the scale required by the current economic and population growth. The most acute environmental damage of our time results from global warming and the loss of biodiversity.

The built environment is of great importance for an ecologically sustainable society, as the construction sector globally consumes about half of all the world’s raw materials and causes about a third of greenhouse gas emissions. From the perspective of a circular economy, there is a huge potential here.

This includes the EU-funded four-year international research project ReCreate (Reusing prefabricated concrete for a circular economy), which studies the reuse of concrete elements, which are deconstructed from buildings slated for demolition, in new construction. Umacon, a top demolition expert, and Consolis Parma, Finland’s leading manufacturer of precast concrete elements, are also involved in the research project.

Umacon renews demolition industry in Finland

The prevailing demolition method in Finland focuses on material recovery, where the secondary raw material materials created through demolition are used in the recycled or otherwise utilized, for example in earthworks. Reusing whole precast concrete elements is rare, even though valuable building parts and equipment, such as building services components, industrial machinery and steel or wooden columns and beams, have been salvaged in Finland in the past. Until now, deconstruction has been driven more by the resale value of building components and equipment than the goal to reduce carbon dioxide emissions.

The reuse of precast concrete elements has not been implemented on a larger scale in Finland before. For Umacon, environmentally friendly and sustainable construction is part of its business values, so applying for the ReCreate research project was a natural choice. The work phases of the deconstruction project had to be planned in a new way so that the elements would not be damaged during the deconstruction work. During the project, new working methods and methods for detaching and lifting elements were developed to ensure that the deconstruction takes place safely and efficiently. Efficient working methods were refined as the project progressed. For example, it took four weeks to deconstruct the elements of the topmost floor, but the last floor was completed in just five working days! The key to a successful project was combining an array of different working methods that had been tried and tested in previous demolition projects into a functional deconstruction process.

Umacon wants to renew the demolition industry in Finland and become a leading company in the deconstruction sector. The success of the ReCreate research project shows that deconstructing precast concrete elements as intact is technically possible. By steering legislation towards low-carbon construction and improving the productivity of deconstruction, deconstruction will mainstream in Finland. Deconstruction and construction are teamwork that require the cooperation of all parties to achieve the goals.

New business for element manufacturer Consolis Parma

Consolis Group is committed to the targets set out in the Science Based Targets initiative. The Group’s global goal is to achieve zero emissions by 2050. The Finnish Consolis company Parma aims to reduce emissions by five per cent annually and halve them by 2035. The most significant means for reducing emissions are the increased use of low-carbon concrete elements, energy efficiency, and the circular economy.

Parma’s low-carbon products are based on substituting cement with binders from industrial side streams. In addition, crushed concrete is utilised in place of virgin aggregates. In the future, one possibility is to supply fully recyclable elements alongside new low-carbon concrete elements.

In the ReCreate research project, the reuse of whole elements is focused on in real life. The elements salvaged from the donor building in Tampere have been delivered to Parma’s Kangasala factory, where they undergo a quality check as well as the necessary modifications and equipment for reuse. The elements that have now been reclaimed were originally manufactured at the company’s factory in Ylöjärvi, Finland, and thus Parma is involved in a research project to promote the reuse of the elements it has manufactured itself.

In this kind of new business, the role of an element manufacturer may include, for example, design, quality control, dimensional changes and equipment, as well as other functions that are suitable to perform alongside new production at the precast concrete factory. Issues to be studied that deviate from new production include approvals, processes and logistics (deconstruction of elements, transfer to the factory, factory-refurbishment measures, transfer of elements to a new site and installation of elements) and environmental permit practices.

by ReCreate project

May 17, 2024

Tove Malmqvist Stigell, Senior Researcher and Docent, KTH Royal Institute of Technology

A transition towards a more circular economy is currently lined up by multiple ongoing policy processes, not least within the EU Green Deal. One novel regulatory development already in effect in a few European countries is mandatory climate declarations and limit values on GHG emissions for buildings. What are these regulations and how do they connect to the re-use of precast concrete elements?

After several decades of development of LCA (Life cycle assessment) methodology for buildings aiming at guiding low-impact design in a life cycle perspective, a raised interest for building LCA has been seen during the latest years. Not least insights on the significance of embodied greenhouse gas emissions in buildings, has led to LCA-based regulations being introduced in several European countries. These require mandatory climate declarations of, so far primarily, new-build projects, and some of them also require building projects to display emissions below a set limit value. Such a climate declaration is a quantitative assessment of life-cycle related greenhouse gas emissions (GHG) of the building that the developer has to perform and hand in to the authority. Countries such as France, Sweden, Denmark and Norway already have such regulations in effect since 2022-2023. In France and Denmark limit values for these emissions are part of the regulation. Such limit values are represented by a set number of kg CO2-equivalents per floor area or per floor area and year, which can be tightened over the years to support further GHG emission reduction. Such limit values are also planned to be introduced in the coming years in Sweden and Finland. The Netherlands introduced a more comprehensive LCA-based declaration with limit value already in 2017. At EU level, the recast of the EPBD (Energy performance of buildings directive) requires a mandatory climate declaration for new-build from 2027 for buildings over 2000 m2 and from 2030 for all buildings, and similarly the EU taxonomy stipulates such a declaration from 2023 for buildings over 5000 m2.

In the light of this type of regulatory development, the interest for developing methods to implement re-use of building components in new-build has increased much. The reason for this is that reuse of components could be one, among other strategies, to ensure low-carbon designs and to comply with tougher limit values in similar regulations. This since re-used components in general have lower environmental impact than virgin ones. To incentivize such strategies further, the Swedish regulation, as an example, makes it possible for a developer to use re-used products “for free”, that is count them as zero impact in the stipulated climate declaration. When setting up the mandatory climate declaration, the Swedish regulation requires a developer to make us of generic data from the national climate data base of Boverket unless EPD´s (environmental product declaration) exist and are used (and also verified that these products were procured to the building at stake). Re–used construction products in Boverkets database are however currently allocated zero GHG emissions, thus incentivizing reused products in new building design. This is naturally a simplification for to create an incentive, but since EPD´s on re-used building components are still extremely rare it would in the current situation not benefit re-use of precast concrete elements to require more detailed information on e.g the emissions of the reconditioning processes. Meanwhile, this type of information is currently built up in the ReCreate project based on the demonstrators in the project.

A central issue of significance in the design of building LCA studies, including the method of LCA-based regulations, is the coverage of processes, that is the system boundaries for the assessments. It is often necessary to omit certain processes due to lack of data or to focus the assessments on known hot-spots. When these types of assessments now enter regulation, different countries take slightly different approaches to the choice of system boundaries which has led to discussions regarding how they then incentivize, or not, certain low-carbon strategies such as circular solutions. For example, the Swedish regulation focus the production and construction stage impacts, that is the embodied GHG emissions of modules A1-A5, according to the European standard EN 15978. In a life cycle perspective, these emissions constitute a significant, and earlier non-regulated, hot-spot. These emissions can also be verified by the completion of a building project, compared to emissions associated with the use and end-of-life stages of buildings. Principally, one could argue that such a more narrow system boundary increase the incentives for re-use of precast concrete elements since the emissions of modules A1-A5 in contemporary construction of buildings are much dominated by the materials of the structure. If implementing more of a whole-life system boundary, as for example is planned for in Finland, the proportional impact of modules A1-A5 will be less, which might reduce the incentivizing effect of re-using building components.

A well-known obstacle to reuse today is the difficulty, and thus the high costs, of dismantling buildings for re–use of elements and components with a viable service life left. This is a question that often comes up in connection to building LCA, with the idea that including the end-of-life (module C) and benefits and loads beyond the system boundary (module D) in the assessment system boundary would incentivize measures taken for design for re-use, including design for disassembly (DfD). However, end-of-life emissions associated with pre-cast concrete elements are much lower compared to emissions associated with the production stages (modules A1-A3) of contemporary construction in the European context, and it may thus be questioned to what extent it´s inclusion could have an incentivizing effect.

An aim with module D is to give room for displaying future potential benefits in form of emission savings due to e.g reuse of components in new constructions, to be reported separately according to the EN 15978 standard. It should be noted that module D highlights potential future savings, the extent of which depend on the future handling of the components, which is hard to predict. The prospects for future re-use improve with DfD implemented, but the calculation of module D is not linked to whether such design strategies were implemented or not. Finally, one needs to remember that both module C and D deals with assessment of potential emissions in a distant future, thus their assessment becomes very uncertain. Normally, these assessments reflect today´s technology, but an increasing number of voices promote that decarbonization scenarios should be applied in similar long-term assessments. If so, the significance of module C and D also decrease.

The proposed Finnish regulation is an example of a more comprehensive system boundary. It for example introduces the “carbon handprint” which more or less reflect an assessment of module D to, in quantitative terms, visualize potential future benefits of re-using the components of the studied building along with other potential benefits of implemented design strategies.

So to sum up, the emerging climate declaration regulations in various European countries do create new incentives to apply re-use of prefabricated concrete elements in today´s new-build. However, to for increased implementation of DfD strategies in today´s new-build for improving prospects for future re-use, these types of regulation do not provide direct and clear incentives. Instead, complementary steering mechanisms might be needed to promote DfD strategies.

Resources:

Boverket climate database in Sweden: https://www.boverket.se/sv/klimatdeklaration/klimatdatabas/

Finnish emissions database for construction: https://co2data.fi/rakentaminen/#en

Example of proposed ongoing regulatory development: the next steps proposed for the Swedish climate declaration regulation: https://www.boverket.se/en/start/publications/publications/2023/limit-values-for-climate-impact-from-buildings/#:~:text=Limit%20values%20can%20be%20introduced,on%20climate%20declarations%20for%20buildings

by ReCreate project

March 15, 2024

Inari Weijo, business development manager (refurbishment), Ramboll Finland

During my master’s thesis work over 15 years ago, I familiarised myself with precast production and its history in Finland. After that, precast concrete has been playing a role in one way or another in my work career. Many projects have involved either repairing precast concrete buildings or building new ones. Since the 1970’s, precast concrete production has formed a significant part of the Finnish construction sector. The systematic and ‘simple’ method provided a standardized way to build, and it quickly became very widespread. The precast concrete system has been criticized for producing a unified stock of buildings, reducing versatility in urban environment and suppressing designers’ creativity. Since the early days, though, the technique spread to erecting ever more complex and monumental buildings. It has been foundational for providing a fast and trusted way for building construction in Finland. There are thousands and thousands of precast concrete buildings here, and some of them are already slated for demolition. A part of the buildings suffers from degradation, but many are just mislocated from today’s point of view.

Figure 1. Finnish deconstruction pilot in Tampere, building vacated before the deconstruction of elements for reuse.

I believe that technical know-how is essential for creativity and enables responsible and sustainable construction. We must be more aware of our decisions’ environmental impacts when building new. Architects’ and engineers’ creativity is ever more challenged as we must prioritize sustainability values. Knowing the technical limitations and possibilities is crucial, so that creativity can be unleashed in the right place at the right time, and adverse uncertainties can be eliminated. Building new is inevitable in the future too, but we need to redefine ‘new’. We must apply regenerative thinking, create net positive solutions and aim for more ambitious circularity. The actions we undertake should have a positive impact on nature and the environment so that instead of consuming it, they restore and revive it. This is a leading value for Ramboll.

Figure 2. Regenerative approach to construction. Image source: Ramboll.

The prevalence of precast technology and the aim for a regenerative effect on environment are two leading thoughts that that drive our ambition here at Ramboll to examine and challenge the present business as usual in the construction sector. The headline’s statement inspires me and my colleagues at Ramboll Finland when we seek to find alternative ways to utilize what already exists. The built environment is a bank of building parts that has technically perfectly fine components stocked in it, preserved intact inside buildings. Only processes and systems to utilize them effectively are needed. I sometimes face people itemising reasons and obstacles why reusing building parts is way too difficult. I believe this pessimistic attitude may well up from the insecurity that follows from the building sector changing dramatically. There may also be a disbelief whether the huge leap, which is necessary, can be taken. Some of the items that the sceptics list are well known, some are relevant, and some are just fictional. We need to keep solving them one by one, showcasing with real-life projects that this is possible and acquire more experience to narrow down the gaping hole between the ‘old’ and the ‘new’ way of building.

An important milestone has been reached when the Finnish cluster finished the deconstruction of the pilot building in Tampere this autumn. We succeeded to reclaim several hundred hollow-core slabs, columns and beams intact, ready for use on next building site. It’s been encouraging to gain good test results, both before deconstruction, through a condition investigation, and after deconstruction, as some of the deconstructed elements have been load tested. All has been well from an engineer’s perspective! Now, the reclaimed building parts are being fitted into prospective new building projects. The search for the new building site has not been stalled because of any technical issues but rather by the currently poor market situation.

That final issue to solve – an important one indeed – is the business model that can support reuse. A circular business needs more collaboration among all the players in the field. Technically we are ready to say ‘yes’ to reusing precast concrete elements!

Figure 3. Reclaimed hollow-core slab, deconstructed from the donor building in Tampere.

by ReCreate project

February 28, 2024

José Hernández Vargas

Architect and PhD student at KTH Royal Institute of Technology

A precondition for reusing precast elements is a correct understanding of the underlying logic of different building systems and the structural interactions between concrete elements. The analysis of existing precast systems starts with a thorough examination across multiple scales, as building layouts, individual elements and their connections are interdependent.

During ReCreate, several precast concrete systems have been identified and studied. While specific pre-demolition auditing and quality control are critical steps towards reusing concrete elements, this ordering of precast elements operates at an earlier and more abstract level, providing a knowledge base for known precast systems that may apply to multiple instances. This task attempts to provide an overview and develop guidelines for the further classification and digitalisation of precast elements as potential material for reuse. Moreover, the information gathered can serve as methodological guidelines for other systems that may differ from the studied cases but follow the same core principles.

When examining technical drawings from historical precast systems it is important to identify patterns that reveal the systematic ordering of the elements. This initial step involves identifying the underlying measurement system from the axes of the building, from which standard layouts can be inferred in discrete modules. Strict repetition patterns can often be found, especially in residential buildings, where building blocks are constituted by the repetition of a building module defined by a staircase. Similarly, this building module can be divided into residential units corresponding to the individual flats on each floor. Each unit defines in turn a defined arrangement of precast elements that can be precisely estimated for each building.

Thus, architectural and structural knowledge of precast buildings is essential for accurately estimating the building stock and potential for reuse of precast buildings. Given the economies of scale involved in this kind of building, the goal of this step is to build a knowledge base to establish workflows for the ordering and analysis of potential donor buildings for reuse.

Building scale

At the building scale, the analysis centres on the identification and classification of precast structures by structural principles and different building types. Precast buildings can be found in all sorts of applications. Yet, despite the wide range of structural solutions they predominantly follow a limited set of basic structural systems. The most prevalent structural frameworks for precast concrete include the portal-frame, skeletal structures, and wall-frame structures. Structural systems for arranging precast structural systems are closely linked to the building types they serve, responding to the intended program’s requirements. For example, portal-frame structures are most suitable for industrial buildings that require large open spaces. Conversely, for residential buildings wall-frame structures are more often the most cost-effective solution as load-bearing walls also separate living spaces. Beyond buildings completely built out of precast components, specialised subsystems can be found for facades, floors and roofs in combination with other structural systems.

System Skarne 66 (Sweden) and their main structural components form the original technical drawings (left) and as a digital 3D model (right)

Component scale

At the scale of individual precast elements, the foremost classification derives from grouping them by their structural role in the structure, i.e., as walls, columns, slabs, roofs, beams, foundations, and stairs that constitute the structure of the building. These categories are based on the Industry Foundation Classes (IFC) Standard (ISO16739-1), which provides a consistent framework for describing elements within the construction industry. These groups can be understood and modelled as variations of the same parametric object, akin to a family of building components. This process is key for building a comprehensive database of precast elements contained in each building.

To further understand the arrangement of elements that constitute a system, the overall dimensions of each element can be plotted to reveal the dispersion of distinct types within the system. In this example, all the elements are aligned in Cartesian space to define the largest dimension on each axis. This method allows the creation of a ‘fingerprint’ of each building, that shows a concise overview of the dispersion of element types and the individual quantities involved. Alignments resulting from common features such as floor heights and standard modules, can also be observed.

Comparison of the ‘fingerprint’ tool showing the types of elements used in System Skarne 66 (Sweden) and BES (Finland). Dot size indicates the number of elements of each type whereas colour corresponds to the main component categories.

Connector scale

At the connector scale, the different relationships between concrete elements can be related to force transfers and security features to ensure the correct and reliable transmission of forces. Connectors are key to ensuring structural integrity by managing structural loads while accommodating additional stresses and strains that arise from thermal movements, residual loads, seismic loads, and fire exposure, among others. A key aspect for evaluating the connectors is the assessment of the alternatives for disassembly and possibly reusing the connector. Analysing precast buildings at the connector scale allows the identification of the compatibility of precast elements across multiple systems from the analysis and comparison of structural details.

Ordering precast systems across these three scales provides a comprehensive picture of how precast systems are conceived, manufactured, and assembled. This knowledge is instrumental for understanding the possibilities that these elements offer for the next building lifecycle. This ordering will serve as the basis for classifying different precast systems into taxonomies and for the digitalisation of existing precast stocks as material for reuse in future projects.

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