KTH - Recreate

January 15, 2025

Arlind Dervishaj, KTH

Concrete is used everywhere—in buildings, cities, and infrastructures. However, due to the large quantities of concrete used worldwide, it contributes to around 8% of global CO2 emissions [1]. While efforts are being made to reduce its carbon footprint, such as by using supplementary cementitious materials, an often overlooked solution is reusing concrete.

The ReCreate project aims to foster a circular economy in the construction industry by reusing precast concrete elements from existing buildings in new construction projects. To support this goal, our study investigated the reuse potential of structural concrete elements, evaluating three key factors: the remaining lifespan of concrete, natural carbonation (ability to reabsorb CO2 over time), and embodied carbon savings achieved by reusing it [2]. Reusing concrete has multiple benefits as it prevents waste, reduces the need for new raw materials, and significantly lowers life cycle CO₂ emissions. However, it is not as straightforward as it looks. The structural integrity of concrete with reinforcing steel can be compromised over the lifetime of buildings, if the right conditions for corrosion emerge, such as from the carbonation of the concrete cover and the presence of moisture at the rebar interface [3].

Circular Construction concept for concrete

Based on established carbonation models, we proposed a digital approach for estimating the remaining service life of concrete elements. The digital workflow also estimates the CO2 uptake from natural carbonation. We tested the workflow on an apartment building with a precast concrete structure, built in Sweden in 1967 during the Million Program. The building was modelled digitally, and material quantities and exposed surface areas of concrete elements were automatically extracted.

Digital workflow and building model

A key aspect of the study was the comparison of carbonation rates specified in the European standard EN 16757:2022 with rates derived from measurements in the ReCreate project and the literature [4,5]. This comparison revealed that the carbonation rates in EN 16757 may be overly conservative and hinder the reuse of concrete elements. We argue that relying on contextual carbonation rates, such as the ones in our evaluation, from a previous condition assessment, and new on-site measurements, is crucial for making informed decisions about concrete reuse. The study also addresses the recent RILEM recommendation on revising carbonation rates in standards like EN 16757 and CEN/TR 17310:2019 [6].

Using carbonation rates from EN 16757:2022, led to the conclusion that most of the precast elements would not be reusable (i.e. carbonated concrete cover and past the initiation phase for service life). The standard assumes a high rate of carbonation for concrete, especially indoors, which reduced the concrete’s remaining service life; concrete cover for indoor elements was expected to carbonate the earliest, 23 years after initial construction. However, when using the contextual carbonation rates derived from the ReCreate project’s investigation and recent literature, all elements were deemed suitable for reuse, with sufficient remaining lifespan. Plaster and other coverings slowed carbonation significantly, extending the service life of concrete. Additionally, carbonated concrete elements can be reused, but further considerations should be made concerning the environment and exposure conditions in the new building. Recommendations from ongoing research in ReCreate are expected for concrete reuse in new buildings.

The study also assessed the CO2 uptake of concrete over its life cycle, including the first service life, a potential storage period prior to reuse, and a second service life when reusing precast elements. The findings indicate that the CO2 uptake estimated using the EN 16757 rates was significantly higher than the estimate based on contextual rates. Additionally, the study demonstrated that the climate benefits of reuse exceeded those of carbonation, which accounted for less than 6% compared to the emissions associated with the production and construction of new precast concrete buildings. This highlights the importance of prioritizing reuse as a key strategy for reducing the climate impact of buildings.

Furthermore, the study investigated the implications of three different allocation methods for assessing the embodied carbon of concrete over two life cycles. The analysis included scenarios with and without carbonation uptake. The results indicated that the Cut-Off method was the most advantageous for reusing the existing building stock, followed by the Distributed approach, while the End-of-Life approach was the least favorable. The study emphasizes that the reuse of existing building stock offers a substantial opportunity for mitigating climate change and fostering a circular built environment.

Comparison of three LCA allocations, over two life cycles

References

[1] Monteiro PJM, Miller SA, Horvath A. Towards sustainable concrete. Nat Mater 2017;16:698–9. https://doi.org/10.1038/nmat4930.

[2] Dervishaj A, Malmqvist T, Silfwerbrand J, Gudmundsson K. A digital workflow for assessing lifespan, carbonation, and embodied carbon of reusing concrete in buildings. Journal of Building Engineering 2024;96:110536. https://doi.org/10.1016/j.jobe.2024.110536.

[3] Angst U, Moro F, Geiker M, Kessler S, Beushausen H, Andrade C, et al. Corrosion of steel in carbonated concrete: mechanisms, practical experience, and research priorities – a critical review by RILEM TC 281-CCC. RILEM Technical Letters 2020;5:85–100. https://doi.org/10.21809/rilemtechlett.2020.127.

[4] European Committee for Standardization (CEN). Sustainability of construction works – Environmental product declarations – Product Category Rules for concrete and concrete elements (EN 16757:2022) 2022. https://www.sis.se/en/produkter/construction-materials-and-building/construction-materials/concrete-and-concrete-products/ss-en-167572022/ (accessed November 26, 2023).

[5] European Committee for Standardization (CEN). Carbonation and CO2 uptake in concrete (CEN/TR 17310:2019) 2019. https://www.sis.se/en/produkter/construction-materials-and-building/construction-materials/concrete-and-concrete-products/sis-centr-173102019/ (accessed September 26, 2022).

[6] Bernal SA, Dhandapani Y, Elakneswaran Y, Gluth GJG, Gruyaert E, Juenger MCG, et al. Report of RILEM TC 281-CCC: A critical review of the standardised testing methods to determine carbonation resistance of concrete. Mater Struct 2024;57:173. https://doi.org/10.1617/s11527-024-02424-9.

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 20, 2024

In this interview, we speak with Kjartan Gudmundsson, an associate professor and leader of WP3 in the ReCreate project, focusing on digital supply chain management and information sharing. WP3 is dedicated to advancing the project’s digital infrastructure, including creating digital models of individual concrete elements. Our discussion will explore how these innovations streamline supply chain processes and enhance data transparency. Join us to gain insights into the cutting-edge digital strategies driving efficiency and sustainability in construction.

Hello Kjartan and thank you for doing this interview! Can you introduce yourself and tell us about your background and role in your institution and the project?

K: My name is Kjartan Gudmundsson. I’m associate profesor at KTH in Stockholm and I’m a leader of work package 3. I’m thrilled to be a part of the project. It’s nice to be a part of something that can promote the reuse of concrete and, eventually, building materials in general.

Can you provide an overview of the progress made in Work Package 3 (WP3) of the ReCreate project so far, and what are the key achievements in the development of data-sharing protocols and digital representations of construction elements?

K: We know how different actors (different specialists in the industry, different stakeholders and actually anyone interested) can capture and share data in a common data environment in a manner that enables other actors in the reuse process to find the information needed to support effective reuse of prefabricated concrete elements. This can support good decision-making, from the early state of doing the inventory of buildings throughout the pre-demolition audit to quality control and towards marketing or the delivery of information needed for a marketplace. This is based on knowing how to name things and how to organize data, how to integrate data and how to make an automated retrieval of the information needed in the reuse process.

We also know how digital tags can be used to track and trace the physical location of physical elements and how the tags can be used to link the physical element to its digital twin and the information linked to the digital twin.

We are in the process of taking inventory of available methods for the reconditioning of concrete elements and how to comply with health, safety, and environmental regulations.

How does WP3 contribute to the broader goals of the ReCreate project in terms of sustainability and resource efficiency?

K: Digital methods for sharing data throughout the value chain will support cooperation of different actors and support decision-making and communication with stakeholders in general and therefore facilitate sustainable and effective use of resources. Having demonstrated this in a realistic process will help illustrate it to the industry in a way that can promote further development.

The common data environment is the infrastructure making this possible while the digital tagging of the building elements makes it easier to follow the elements throughout the supply chain while the tags also make it possible to link the successively collected data to the digital model. We will also be looking at the physical processes of reconditioning the elements. Practical examples of use and full-scale testing and the involvement of industrial actors will of course strengthen the value of this contribution.

Could you explain the role of Radio Frequency Identification (RFID) technology in WP3 and how it is used to facilitate digital supply chain management and information sharing in the project?

K: We have already done a comprehensive study that shows how RFID technology as well as a number of other technologies make it possible to tag the physical elements so that we can see the location and movements of the buildings elements. One actor puts a tag on the element, the elements travel to the next place and movements are registered. Any actor with access can then read off that information.

As I said the tags can also be used to pair the building elements to their digital representatives so that the tag can be used to access a digital inventory containing information about the elements such as historical information, results from pre-demolition audit, results from quality tests and finally a material passport containing the information needed for effective reuse.

Can you share some insights into the development of a common data environment (CDE) for storing BIM data and digitized information? What challenges were encountered in creating this central repository?

K: Our work provides an overview of available solutions for Common Data Environments (CDEs) that can enable effective storing and sharing of data that is captured and created. We have also discussed how data and files can be named and stored in a manner that enables automated retrieval of files and information. The basic principle is that knowing the naming principles for files and how the data is organized in those files will give the user the possibility to search for and collect the information needed. An important feature is that we want to be able to control the access and authorisation to the different files and documents while this access can also depend on the stage of the process, from work in progress to the sharing of data across teams to published files and archived material.

This includes the use of the current platform for sharing information in the research project. We look forward to further development of digital protocols for capturing and sharing data that will support decision making throughout the reuse process, such as historical information, data from pre-demolition audit and quality assurance to give just a few examples.

Interoperability or the ability of different software to exchange data is a big issue and to some extent a challenge. In a way, there is a trade-off between using open platforms and their application programming interfaces (APIs) that allow for customisation of functionalities and the using of more well-developed software platforms.

WP3 involves creating digital models of individual elements. Could you elaborate on the process of generating these digital models, including the use of Industry Foundation Class (IFC) as an open file format?

K: The digital elements are generally created using well-known proprietary design authoring tools for 3D modelling. The main process is to create those elements with data from existing drawings. The purpose of using the IFC open file format is to make the models accessible across different software platforms. Another reason is that the IFC files have a well-defined data structure or schemas that makes them less sensitive to the software versions used. You can in fact read the files with a number of freely available IFC viewing tools and even read them with just a few lines of own computer code.

How does WP3 ensure that the information collected from the digitalization of elements is used effectively, especially in supporting the needs of designers as mentioned in WP5?

K: By having a well-defined definition of the data needed throughout the process from quality control to design we can make sure that the digital elements either have the information needed or at least a place to store that information or a link to it when it has been collected. Firstly, we have to know what is the data needed. Secondly, we have to know how to make that data accessible. So, people using different software platforms can still retrieve that data and use it for its own purposes.

Sustainable methods for stripping and cleaning elements are part of WP3’s objectives. Can you discuss the methods being developed and how they comply with health, safety, and environmental regulations?

K: This task is concerned with developing methods for cleaning and stripping deconstructed elements from old plastering, paints, tiles, wiring and wallpapers and for cutting and refurbishing components and retrofitting them for new designs. The first stage of this task is to make an inventory of currently available methods. We will also look at and evaluate different methods for cutting such as with track saws, flats slab saws or CNC robot cutting.

All the methods must comply with rules and regulations concerning health and safety in the workers environment. This includes a limit value for dust and the use and handling of solvents. This also includes methods for ventilation as well as methods for sealing off working zones. The methods must also comply with environmental regulations.

What is the significance of evaluating the cost efficiency and sustainability of the methods for cleaning, stripping, and refurbishing components? How do these methods contribute to the circular economy?

K: By evaluating the efficiency and sustainability of methods for cleaning, stripping, and refurbishing, we provide the industry with a list of available methods that can help promote reuse as a possible alternative. We would like to show how those methods comply with regulations concerning health and safety. Reconditioning is an essential part of the process. By showing how it can be done, it is more likely that people will tap into that and want to be a part of the process.

RFID-aided logistics is a crucial aspect of WP3. Could you provide examples of how RFID technology is applied in practical pilots within the project, and how it impacts the logistical processes?

K: We have already done some laboratory tests to check out how the electronic tags can be attached to the physical elements and how they might be protected as well as how factors can affect the readability of the tags. We have also been looking at different digital technologies for connecting the tags to databases and building information models.

The next step is to do some field tests of different tags to find out how they perform in different real-life scenarios in a logistic process. After that, we will be evaluating a selected number of technologies in the pilot projects of the different country clusters. The purpose of those tests is to see how well they can be used to register the travel of the elements but also how the tags can be used as the means to connect to a digital model for retrieval and uploading of relevant information.

Finally, could you highlight the key deliverables of WP3, including the common data environment, RFID-aided logistics, and the processing of deconstructed components? How will these deliverables benefit the construction and AEC industry in the long run?

K: The common data environment plays an important role in making information available to different actors and stakeholders in a reuse process. Our deliverable includes a description of the fundamental principles of making data accessible in common repositories but also on how to ensure interoperability (or how to make that data useful across different software platforms) and the benefits of using open file formats. We will illustrate those methods and principles through practical examples such as by showing how different kinds of data are stored and used to create a digital model and how that model can be populated with data from the various stages of the reuse process.

One objective of our work on RFIDs and tags is to show how the tags can be used to follow and register the location and movement of the elements. In addition to that, we will show how the tag can provide a link to digital information associated with the element. Until now, we have done quite a comprehensive literature study of the available technologies for tagging prefabricated concrete elements. In essence, this means that we have compared the functionalities of different tag technologies such as QR codes, active and passive RFIDs, NFCs and Bluetooth. This comparison includes the reading range and ability to store and retrieve data as well the possibilities to use widely available handheld instruments such as mobile phones but we have also done tests on different methods for attaching the tags to concrete and how this may affect the performance of the tags.

We want to deliver a range of applicable methods for the processing of deconstructed components. As I mentioned earlier it is important that those methods are sustainable and economically feasible but also that they can be implemented in compliance with regulations concerning health and safety.

In general, our cooperation with industrial partners and tangible examples of implementation that include full-scale testing in the pilot studies are central to the relevance and quality of our work and deliverables.

What inspired you to become involved in the ReCreate project, and can you share a bit about your personal background and interests that have shaped your role as the WP3 leader?

K: My background is in building technology or architectural engineering with some focus on how to construct buildings and how to evaluate building performance such as in terms of energy use and environmental effects. Recreate is to me a part of the transition towards more sustainable construction and with my interest in Building Information Models (BIM) and digitalization; it is very interesting to investigate how digital technologies especially can be used to facilitate the reuse process. I would like to show how it can be more effective and how can we gather information and evaluate and analyse things. Having the possibility to put the theory and methods to the test in a practical context is also a very valuable factor.

Would you like to give some conclusion to wrap up everything that WP3 does or ReCreate project is itself?

K: Great thing is to meet all the people involved and to realise what you can do with such a good team.

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

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.

by ReCreate project

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.

by ReCreate 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 41^st 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 & 40^th 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.

References:

[1] Dervishaj A, Fonsati A, Hernández Vargas J, Gudmundsson K. Modelling Precast Concrete for a Circular Economy in the Built Environment. In: Dokonal W, Hirschberg Urs, Wurzer G, editors. Digital Design Reconsidered – Proceedings of the 41st Conference on Education and Research in Computer Aided Architectural Design in Europe (eCAADe 2023), Graz: eCAADe, TU Graz; 2023, p. 177–86. https://doi.org/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.

[3] Dervishaj A, Hernández Vargas J, Gudmundsson K. Enabling reuse of prefabricated concrete components through multiple tracking technologies and digital twins. European Conference on Computing in Construction and the 40th International CIB W78 Conference, vol. 4, Heraklion: European Council on Computing in Construction; 2023, p. 1–8. https://doi.org/10.35490/EC3.2023.220.

[4] Jansen M, Gerstenberger B, Bitter-Krahe J, Berg H, Sebestyén J, Schneider J, et al. Current approaches to the digital product passport for a circular economy: an overview of projects and initiatives 2022;198. https://doi.org/10.48506/OPUS-8042.

[5] European Commission. Transition pathway for Construction 2023. https://ec.europa.eu/docsroom/documents/53854 (accessed March 17, 2023).

by ReCreate project

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.

THE STATE OF REUSING CONCRETE IN SWEDEN

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.

ON THE SWEDISH PILOT SITE

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.

by ReCreate project

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.

by ReCreate project

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.

Older Posts

KTH - Recreate

Reusing Precast Concrete for a Sustainable Future: Evaluating service life, carbonation and carbon footprint

Exploring an informed design process in the reuse of structural concrete elements

Focusing on digital supply chain management and information sharing – interview with Kjartan Gudmundsson

New climate regulations and re-use of precast concrete elements

Ordering precast knowledge: A multi-scale review of precast concrete elements.

ReCreating the building sector future toward net zero emission with precast concrete reuse

Digital Reuse: Leveraging technology for a circular built environment in the age of AI

Erik Stenberg on the business case for reusing concrete elements

Erik Stenberg weighs in on the reuse of concrete in Denmark and elsewhere

KTH presents its pilot building made of recycled concrete

EU project on recycling of concrete elements

Challenge for architects

Division Selective Deconstruction - Building in Existing Contexts (ECOSOIL Ost)

Prof. Angelika Mettke is reshaping concrete futures—one element at a time

Researching prefabrication and housing in the Czech Republic

EU FUNDING

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