KTH Archives | Recreate

December 8, 2023

Ahmad Alnajjar, PhD student at KTH

ReCreate project is a forward-thinking initiative that explores the reuse of precast concrete elements from various angles. A key aspect of this project is evaluating the climate benefits from a life cycle perspective. Our recent work, particularly in the Swedish pilot construction, has shown promising results in reducing embodied carbon – a crucial step in sustainable and circular building practices. About 92% of embodied carbon was avoided at the building level which is largely attributed to the reuse of concrete elements, including precast concrete elements. This achievement aligns with previous research highlighting the benefits of reusing precast concrete and further emphasizes the reuse’s effectiveness in mitigating the environmental impact of construction. Unlike most previous studies, the embodied carbon evaluation of the Swedish ReCreate pilot project stands closer to real-world applicability. It is based on field experiments conducted by seasoned professionals in the building sector, adding practical validity and depth to our findings.

An important facet of our findings in the ReCreate project underscores a significant advantage in the reuse of whole precast concrete elements over traditional recycling methods. Through our comprehensive analysis, it has become evident that the embodied carbon savings achieved by reusing entire elements are considerably greater than those realized by merely crushing to recycled concrete aggregate and shredding the rebar to steel scrap. This distinction is crucial, as it highlights the substantial environmental benefits of reusing structures in their complete form. By opting for reuse over recycling, we not only retain the material’s inherent value but also significantly reduce the carbon footprint associated with the production of new building materials.

Our assessment has also brought to light interesting insights. Contrary to common concerns, we found for example that the transportation of reused elements does not significantly add to the project’s carbon footprint, as it is comparable to the transport distances of new building materials. We hope that this finding will encourage building industry actors to reconsider their material sourcing strategies, recognizing that incorporating reused elements can be both environmentally beneficial and logistically viable.

Currently, our team is focused on comprehensively understanding the future availability and demand for pre-used precast concrete elements. We are assessing both the timing of their availability and the quantities that can be effectively reused in new construction projects. By addressing these critical aspects, we aim to elucidate the role that reusing precast concrete elements can play in meeting Sweden’s and the EU’s ambitious climate goals.

Through the ReCreate project, we are exploring new avenues in construction, aiming to make a meaningful contribution to sustainable building practices. Our team is dedicated to not only implementing these innovative practices but also to rigorously documenting and analyzing our findings. Our research will soon be available in various scientific journals, providing a detailed and scholarly overview of our work and its implications for sustainable construction. Keep an eye on our progress as we delve further to uncover the potential and challenges of this innovative approach and look out for our publications to gain a deeper understanding of the impact and scope of our project.

September 27, 2023

Arlind Dervishaj, architect and doctoral researcher at KTH Royal Institute of Technology

The use of digital tools for the design of buildings has become a common practice for architects and engineers alike, commonly referred under the umbrella term digital design. The range of digital tools at our disposal and their utilization has been growing, with reference to Building Information Modelling (BIM), environmental design tools, computational design plugins, and optimization algorithms. Additionally, 3D printing, robotic fabrication, virtual reality, and Artificial Intelligence (AI) are becoming more commonplace not only in research environments but also with practical applications within the architecture and engineering fields. Despite these advancements that have made it easier to design and assess the sustainability of projects, buildings remain a major contributor to climate change, responsible for 37% of global carbon emissions, half of all extracted raw materials, and waste generation due to construction and demolition activities. In light of these challenges, the circular economy concept presents a promising solution, with digital technologies playing a crucial role as enablers.  The importance of reevaluating the relationship between design and the digital became the focus of the 41st eCAADe (Education and Research in Computer-Aided Architectural Design in Europe) conference hosted at TU Graz under the theme Digital Design Reconsidered.

At eCAADe 2023, I presented a refereed paper, with co-authors Arianna Fonsati, José Hernández Vargas, and prof. Kjartan Gudmundsson [1]. The paper is titled Modelling Precast Concrete for a Circular Economy in the Built Environment with subtitle Level of Information Need guidelines for digital design and collaboration. This was also the first presentation in the eCAADe session on BIM & Sustainability. I kicked off my presentation by captivating the audience with striking examples of AI-generated buildings crafted from reclaimed concrete elements, setting the stage for an important question to follow.

Can we design buildings with reused elements simply with a text prompt and AI or is there more to consider?

Before the design process, the practice of reuse involves a series of essential steps, which encompass, among other things, the identification of suitable buildings and components for reuse, the process of deconstruction, the management of storage, and the implementation of quality assurance measures. Reliable and up-to-date information is crucial in supporting designers and stakeholders in making decisions for circular construction. Various data capture methods for buildings exist to facilitate their identification and potential reuse. These methods encompass technologies such as laser scanning, photogrammetry, scan-to-BIM workflows, and machine learning algorithms. Examples of the latter include identifying materials and components at urban and building scales, and some even automate the creation of 3D models from point clouds.

Nevertheless, a substantial gap remains within the literature with relevance for practice concerning the specifics of required data and the process of sharing and requesting information to enable reuse and collaboration of different parties. To address this challenge, we developed a set of digital reuse guidelines tailored specifically for precast concrete. These guidelines are based on the Level of Information Need (LOIN) standard EN 17412-1:2020 [2], and are informed by our experience in the ReCreate project, which includes construction pilots conducted in Sweden (Swedish pilot at the H22 City Expo) and in partner countries. Our study not only embraces the EN 17412 standard but also takes it a step further by extending its applicability for digital reuse in circular construction. These guidelines are designed to enhance the reliability of information across the reuse process and construction cycles. They introduce innovative concepts, such as the creation of digital templates that evolve into digital twins of reused precast elements. Furthermore, they can be used for specifying information requirements for reused as well as for newly produced elements. Additionally, as part of our comprehensive approach, we have included a comparison of the geometrical modelling aspects of LOIN in two widely used CAD and BIM software platforms, Rhino and Revit.

Currently, our ongoing research within the ReCreate project continues to explore and expand upon various aspects that can relate to the LOIN framework. As an example, another recent paper authored by me, José, and Kjartan was presented at the 2023 EC3 & 40th CIB W78 conference in Crete, Greece [3]. This paper explores the timely theme of tracking and tracing building elements, where more background information can be found in the literature [4], [5]. We present a novel digital workflow for modelling various tracking tags in the BIM model such as QR codes, Radio Frequency Identification (RFID), and Bluetooth. Moreover, we present promising results from laboratory tests that, arguably for the first time, explore the utilization of Near Field Communication (NFC), which is a subset of RFID, and its integration with Bluetooth technology.

More facets on the topic of reuse are being investigated within ReCreate that will further demonstrate the applicability and potential of digital reuse in creating a circular built environment. Our research encompasses a wide spectrum of considerations, including data capture and sharing methods, material passports, destructive and non-destructive testing of concrete structures, and innovations in the design processes. These ongoing efforts aim to advance sustainability and circularity in the built environment through the integration of digital technologies.


[1] A. Dervishaj, A. Fonsati, J. Hernández Vargas, and K. Gudmundsson, “Modelling Precast Concrete for a Circular Economy in the Built Environment,” in Digital Design Reconsidered – Proceedings of the 41st Conference on Education and Research in Computer Aided Architectural Design in Europe (eCAADe 2023), W. Dokonal, Hirschberg Urs, and G. Wurzer, Eds., Graz: eCAADe, TU Graz, Sep. 2023, pp. 177–186. doi: 10.52842/conf.ecaade.2023.2.177.

[2] European Committee for Standardization (CEN), “Building Information Modelling – Level of Information Need – Part 1: Concepts and principles (EN 17412-1:2020),” 2020 Accessed: May 18, 2022. [Online]. Available: https://www.sis.se/en/produkter/standardization/technical-drawings/construction-drawings/ss-en-17412-12020/

[3] A. Dervishaj, J. Hernández Vargas, and K. Gudmundsson, “Enabling reuse of prefabricated concrete components through multiple tracking technologies and digital twins,” in European Conference on Computing in Construction and the 40th International CIB W78 Conference, Heraklion: European Council on Computing in Construction, Jul. 2023, pp. 1–8. doi: 10.35490/EC3.2023.220.

[4] M. Jansen et al., “Current approaches to the digital product passport for a circular economy: an overview of projects and initiatives,” vol. 198, 2022, doi: 10.48506/OPUS-8042.

[5] European Commission, “Transition pathway for Construction.” Accessed: Mar. 17, 2023. [Online]. Available: https://ec.europa.eu/docsroom/documents/53854

November 7, 2022

Leader of the ReCreate Swedish country cluster Erik Stenberg had another interview where he outlined the importance and advantages of the project.

The advantage of the concept is that the climate footprint and amounts of waste are radically reduced as it is much better to reuse entire elements than to grind down the concrete and use it as filling material, says Erik Stenberg.


Today, concrete elements are very rarely reused. At EU level, the figure is zero percent and in Sweden there are a few isolated examples. This is mainly because it is cheapest and easiest to build with new concrete. The business models for reuse do not exist and all parts of the construction sector are adapted to new materials, says Erik Stenberg. The goal of KTH researchers will be to examine the business chain for the reuse of concrete elements in the Swedish context and how it is affected by processes and regulations in the construction sector. Sweden actually has good conditions for reusing concrete elements because we built a lot with prefabricated concrete in the 1960s to 80s. Even if the elements are not manufactured to be taken apart and used again, according to Erik Stenberg, this is entirely possible.


The pavilion that the researchers built and displayed during H22 was a successful sub-project. The building consisted of 99 percent recycled material and the climate footprint had been reduced by 90 percent. The mistakes made gave the researchers new insights, for example that concrete must be handled carefully. The reuse also led to unexpected architectural solutions.

The elements were larger than we imagined, which resulted in a sturdier building. Solutions around doors and windows had to be adapted to this and the house’s pillars got a new design when they proved to be too heavy for the slab. Instead of being seen as obstacles, the limitations can contribute to interesting architecture, says Erik Stenberg.

Erik Stenberg also maintains a studio where students design buildings based on the concept in the research project. Erik Stenberg says that the students have shown that it is possible to design houses with good layouts and good light conditions from recycled concrete elements and that it is possible to design both row houses and point houses with elements from slatted houses.

October 5, 2022

Erik Stenberg, a lecturer in architecture at the KTH School of Architecture and leader of the Swedish ReCreate country cluster, investigates the current practices of the reuse of precast concrete in the world.

He posits that offices with prefabricated concrete structures are the most common buildings that are demolished today, most often for housing construction, and that concrete from those demolished buildings is simply ground and that we create an unnecessarily big impact on the environment by doing so.

”When recycling, the product is changed and used for something else, or in the same area of use. When we are reusing, it is used once more in the same form and design.”

– “I’m afraid that someone will think that, like in Denmark, we will start grinding programs worth millions. It would be capital destruction because the houses are built with quality and will last at least another 150-200 years if they are dry and warm.” said Erik Stenberg.

According to him, Denmark also failed to meet the goal of reusing building elements in projects, in order to incorporate a better local history for residents, because the EU directive is that at least 70 percent of a building’s weight must be reused during demolition. However, in the Swedish ReCreate pilot study, the figure dropped to a staggering 99 percent!

He concluded that there were some mistakes in the project, but now they know where the obstacles lie in the construction permit phase, how access and quality can be ensured, and how the concrete elements can be reassembled, which enables an immediate reduction of carbon dioxide in new production.

June 10, 2022

In the middle of Drottninghög, researchers from KTH are building a pilot building in the form of a pavilion from recycled concrete. The building is part of the H22 City Expo fair, which takes place between 30 May and 3 July.

The building stands on a plot where a preschool previously stood. KTH researchers have been able to use the base plate from the preschool for the building, which is 8×22 meters wide, 4 meters high, and consists of a few hundred tons of concrete. The building consists of 99 percent recycled material.

”The production of new concrete is very resource-intensive and accounts for 3-4 percent of the world’s total carbon dioxide emissions. By using recycled concrete in new buildings, emissions could be radically reduced. Our calculations show that by using recycled concrete in our pilot, we get a reduction of the carbon footprint by 96 percent compared to if we would have used new concrete. So this recycling of concrete points to a way forward.

Today, office properties are demolished from concrete that is perhaps 40 years old to make room for new homes. But that concrete has a much longer technical life than that, 100, 200, maybe up to 300 years as long as it is hot and dry. And if we are to access the carbon dioxide consumption in new buildings, we must have access to these heavy concrete frame elements.” – says Erik Stenberg, professor at the KTH University.


EU project on recycling of concrete elements

Professor Stenberg also leads the Swedish part of the EU project ReCreate – Reusing Precast concrete for a Circular Economy – whose purpose is to investigate how to reuse concrete elements in new buildings. The project, which is funded by the EU’s Horizon 2020 program, is led by the University of Tampere and the initiative also includes Eindhoven University of Technology and Brandenburg University of Technology.

Within the framework of the project, all four participating universities will produce two pilots – one digital and one physical. Unlike Tampere, Eindhoven and Brandenburg, KTH started with the physical pilot, the one that is now shown in Helsingborg, and will then make a digital one. The three partner universities’ first digital pilots can be viewed in the form of 3D-printed models of each donor building in KTH’s pavilion pilot.

There will also be descriptions of the various projects. But the exhibition’s focus is on Helsingborg and Drottninghög. Among other things, we present a project on recycling concrete in Drottninghög that some of our students at the School of Architecture worked on last autumn, says Erik Stenberg.


Challenge for architects

In addition to his role as leader for the Swedish part, he works with historical analyzes and a mapping of where concrete elements are, when and where they were built, in what form, by whom and for what. Two more KTH researchers are involved in the project – Kjartan Gudmundson from the Department of Sustainable Buildings and Tove Malmqvist from the Department of Sustainability, Evaluation and Governance, SEED.

Kjartan Gudmundson looks at issues such as quality assurance – concrete quality and the presence of hazardous substances – and digitization of historical and new information about concrete elements that can accompany them when they are used again, while Tove Malmqvist works with issues such as life cycle analysis, climate impact, business models, and regulations.

April 29, 2022

Erik Stenberg, architect and senior lecturer in architecture at KTH – School of Architecture and the Built Environment (ABE) in Stockholm, answered a few questions on why reusing concrete is important in urban development projects.


Why is the reuse of concrete important?

– This is where the biggest environmental benefits can be made. If you access the concrete in the structure of houses, you can achieve the largest reduction in carbon dioxide.


 Why is it important in urban development projects?

 – It is becoming more and more important to look at the entire life cycle and carbon footprint of the entire urban development and not just individual buildings. We have to look at what was there before and what will come after. We need to make better use of the resources that are already above ground. Also, the historical dimension has nothing to do with carbon dioxide pollution, but with cherishing a legacy, taking advantage of what is good and building on it, and improving what needs to be improved.


What are the benefits of using reused concrete?

– This is exactly what we test in ReCreate. The thesis is that the concrete continues to harden during its lifespan and the technical lifetime is much longer than the service life of the buildings. Therefore, reused concrete should be better than new concrete both constructively and environmentally as we do not use and extract resources from the earth’s crust.


So concrete is made to last longer than the time we use it today?

 – It lasts much longer. The concrete you usually see is the one that is exposed outwards to the external elements and it is usually hit harder by rain, weather, cold, or salts (depending on where it is) than concrete that has been sitting hot and dry. If the concrete is hot and dry, it lasts forever.


What opportunities do you see when it comes to reusing concrete?

 – I look at the material and historical values and that we get a healthier discussion about how urban development should be done, and that we consume fewer resources when we build in the future. This is the biggest change that needs to happen, not just thinking ‘new’ all the time but rather that we take care of what we already have.

March 2, 2022

Tampere University researchers from WP 7 in Finland visited KTH and the Swedish country cluster in Stockholm in October 2021

Two researchers, Linnea Harala and Lauri Alkki, from Tampere University Work Package 7 in Finland visited KTH and the Swedish country cluster in Stockholm in October 2021. The research of Work Package 7 focuses on the business aspects within ReCreate and the first research deliverable focuses on mapping the local ecosystems of concrete element reuse. The examination of these ecosystems was initiated in summer 2021 within the Finnish Country Cluster by research interviews and ethnographic follow-up. After we had gained a basic overview of the actors, their linkages and ecosystem structures within the Finnish country cluster, we expanded our ecosystem research activities to the Swedish country cluster.


During the research visit to Stockholm, Linnea and Lauri were warmly welcomed to KTH by the Swedish country cluster. This first research visit included formal and informal activities facilitating to get to know each other during meetings, campus tours and delicious lunches. The main research activities included research interviews with the key ecosystem actors and ethnographic follow-up on a reference project site visit and during the Swedish country cluster meeting. However, in addition to these research activities, networking and exchanging knowledge between the country clusters was also of great importance for the collaboration between the Finnish and Swedish country clusters.


ReCreate’s first cross-country cluster research visit exceeded our expectations and laid the groundwork for international future research collaboration within ReCreate. International collaboration was soon initiated as at the beginning of 2022 researchers from the Finnish country cluster started a joint research publication project together with researchers from the Swedish country cluster. This article aims to create an understanding of the concrete element reuse ecosystems in Finland and Sweden. All in all, this research visit was a great way to initiate cross-country cluster collaboration within ReCreate, exchange ideas and knowledge and ultimately improve ReCreate’s influence to maximize impact.

Photo credit: Hanna Kalla, KTH


“This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 958200”.

Follow us: