Jukka Lahdensivu - Recreate

May 12, 2026

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Authors: Aapo Räsänen and Jukka Lahdensivu, Tampere University

Introduction to the reports: Procedure for quality management of reclaimed concrete elements, Properties and quality of precast concrete elements deconstructed in ReCreate’s pilots and Quality management best practices in reuse of precast concrete elements of the ReCreate project. The full reports are available on the website.

The ReCreate report Procedure for quality management of reclaimed concrete elements presents the six stages process for safe reuse of reclaimed concrete elements as a part of bearing structures in new buildings. The key process stages are:

Pre-deconstruction audit, where the main actions are finding out the type and number of elements, assessing their reuse potential, and gathering information for the next stages.

Structural investigation, where the main actions are ensuring material properties of elements primarily with non-destructive (ND) or semi-destructive (SD) methods, determining the condition of the elements, and finding out the existence of possible hazardous substances.

Deconstruction design and execution, where the determination of safe deconstruction and lifting methods is the main action, together with transportation and storage of deconstructed elements.

Full-scale testing is carried out if the structural capacity of reclaimed elements cannot be uncovered through other means or if there is doubt about safety factors. Also newly developed retrofit connections need testing if original connections cannot be reused.

Redesign and reassembly, where the main actions are designing the reclaimed elements according to Eurocodes and standards in force. Also, the refurbishment of the reclaimed elements must be designed and carried out before delivering elements to new construction site.

Product approval and authorisation is the final stage, where documents from the previous stages, together with technical drawings and calculations, will be presented to authorities to obtain official permits for reuse.

Visual investigation and thorough documentation are an essential part of each stage. Information must be carried through from stage to stage.

Properties and quality of reclaimed elements

Properties and quality of reclaimed elements were determined in four piloting countries: Finland, Germany, the Netherlands and Sweden. The report provides description of used test methods number of samples and measurements, and all test results carried out in laboratories of each donor buildings. In short, concrete grade used in reclaimed elements was higher than original design value, the elements were in good condition in general, and all found harmful substances could be removed before detaching of elements.

Knowledge Level

The ReCreate report Quality management best practices in reuse of precast concrete elements focuses on test methods and sufficient number of tests/samples needed for determining the material properties of concrete and the bearing capacity of elements. The actual condition, material properties, remaining service life, and probable repair needs of elements intended for reuse can be assessed through a systematic investigation. The need of testing depends strongly on the extent of available information. Therefore, four Knowledge Levels (KLs) are introduced:

Knowledge Level 1 (KL1): No information is available regarding the concrete quality, reinforcement properties, or the manufacturer of the elements.

Knowledge Level 2 (KL2): No information regarding the material qualities is available, but the manufacturer is known.

Knowledge Level 3 (KL3): Some specifications describing the concrete and reinforcement properties of the elements exist, but no further information about the manufacturer or quality control applied during production is available.

Knowledge Level 4 (KL4): Detailed archives of specifications describing the used concrete quality and reinforcement steel design are available, and both the manufacturer and its quality control system are well-documented.

The first two knowledge levels (KL1 and KL2) describe situations where no design specifications are available on the donor building. In these cases, extensive non-destructive testing (NDT) and destructive testing (DT) is required. For KL3 and KL4, partial or complete archives of original documents are accessible, and the specified properties only need to be verified through selective testing, reducing the workload.

Parallel test methods

Many different test methods are available for determining properties of concrete elements. Some methods are simple, while others are more complex, potentially causing more damage and costs. Additionally, the reliability of the tests varies depending on the method used. The testing methods used should always selected to suit each specific situation, based on the project’s criteria. The criteria may include, e.g. the type of element, required level of reliability, requirements of the new building, or the test methods available.

Ideally, the test methods should be selected to maximise the amount of knowledge gained while minimising costs and time. By using parallel test methods, reliability can often be improved by complementing each method’s shortcomings to create a more reliable aggregated method. In the report different test methods are presented for:

compressive strength evaluation of concrete

cover depth and diameter measurements of reinforcement

carbonation measurements of concrete

chloride content of concrete

corrosion of reinforcement

freeze-thaw resistance of concrete

deteriorated concrete.

The methods are presented in tables containing information on suitable standards, representativity, reliability, workload and number of needed tests of each presented test methods when the information is available.

Number of samples

Number of samples needed for each test are mentioned in standards in the first place. Several tests presented in report have no standard, e.g., cover depth measurements reinforcement. Sufficient number of test specimen or full-scale tests for high reliable results is based on scientific research on the results from the pilot projects. High deviation of test results gives a recommendation of higher number of samples/tests than the minimum number in standards. The recommended number of samples are presented in the report.

Conclusion

Quality assurance measures carried out in the ReCreate project varied somewhat across different pilots. The best practices presented in the report are based on the necessary actions taken at each pilot. In particular, damage and deficiencies in structural elements required significant interventions. These defects were discovered at different stages of the pilots, leading to immediate responses each time, which resulted in multiple actions being taken.

Overall, the quality assurance measures are especially useful in validating the reusability of elements. These measures will also benefit the structural designers by helping anticipate potential deficiencies and necessary modifications during refurbishment. Well-documented processes will provide evidence of reusability to authorities and other stakeholders involved in the reuse process. In Finnish pilots the developed quality management process was used successfully. The building inspection authorities in Tampere and Helsinki accepted the developed quality management process for reused concrete elements as a part of the site-specific authorisation.

by ReCreate project

November 26, 2025

In this interview, we are speaking to Jukka Lahdensivu from Tampere University, whose work lies in WP4 in the ReCreate project. WP4 is focusing on new safety standards for reusing precast concrete components to promote sustainable construction practices. It captures the technical challenges and the practical goals of balancing safety, regulatory standards, and sustainability in the reuse of materials.

Can you explain the primary motivation behind creating a new quality management process for deconstructed precast concrete components?

Jukka: The primary motivation, in my view, is to demonstrate to customers and authorities that reclaimed components can be safely repurposed. It’s essential to ensure these elements meet safety standards when reused, and that’s why we’ve developed this process to verify their viability. We’re actively studying various aspects of these materials to ensure reliability.

How does this process differ from existing practices for virgin materials?

Jukka: There are quite a few similarities. In a factory setting, you test the raw materials, like cement and aggregates, before creating concrete and verifying it meets quality standards. However, for deconstructed materials, we’re testing the structure itself, often on-site, which is a big departure from standard practice with new materials. New components are generally tested during manufacturing, but here, the focus is on validating reclaimed components in their current state.

How challenging was it to integrate the investigation of harmful substances into the pre-deconstruction audit? What obstacles did you encounter in developing a standardized procedure for this?

Jukka: It wasn’t particularly difficult, especially since building renovations often require these studies before demolition. Finland, in particular, has a heightened awareness of harmful substances, likely because of extensive media coverage and prior issues with building materials. We’ve taken a thorough approach here, often exceeding regulatory requirements to ensure safety.

So, you would say people in Finland are more aware of these substances?

Jukka: Probably. It’s discussed frequently in the media, and we’ve faced issues in some newer buildings due to materials being enclosed prematurely. These problems have led to a deeper understanding and greater caution regarding harmful substances.

Work Package 4 focuses on ensuring reusable elements meet material and structural standards. Can you describe the testing process for these elements and their role in maintaining safety?

Jukka: We conduct tests on material properties before deconstruction to confirm the elements can be reused safely in new projects. This includes taking core samples for compression strength testing, measuring concrete cover depth over reinforcement, and conducting full-scale tests on beams and hollow-core slabs in the lab. These tests align with existing standards, ensuring consistency.

What are the key differences between assessing deconstructed versus newly manufactured components?

Jukka: With new concrete structures, we know the exact composition of materials. We need to analyse the concrete strength, reinforcement type, and other specifics for existing buildings. This lack of prior knowledge is the main difference when evaluating reused materials.

In this work package, you mention variability in material properties due to inhomogeneity. How do you manage these variations during testing?

Jukka: We conduct multiple parallel tests to gather a distribution of results. This approach is similar to testing new materials, but in a factory setting, components are consistently produced. With reclaimed materials, we often have only a few components to test, which means sample sizes differ from typical factory conditions.

Could you elaborate on potential challenges, such as deterioration, during deconstruction, transportation, or storage?

Jukka: We detected most deterioration, like cracking, in hollow-core slabs after deconstruction. These cracks weren’t visible in the building but appeared after detachment, likely due to the removal process. In Finland, we’ve also had cases where water entered hollow-core slabs, froze, and caused cracking. We had about six slabs damaged this way. When we removed the levelling on top of these slabs, accidental holes were created in the slab decks, though this was rare. In storage, however, we didn’t encounter any issues.

How do you decide on the reuse of these cracked components?

Jukka: It depends on the severity of the cracks. Small cracks with a width of 0.1-0.2 mm are often acceptable for reuse. Larger cracks, 0.3-0.5 mm or wider, need further assessment. We’ve created guidelines for visual assessment in the factory, and if significant cracking is found, a construction designer reviews it to decide on further action.

What are the most significant technical or regulatory hurdles in obtaining approval from authorities for reused components, and how might these be addressed in the future?

Jukka: The main hurdle is that authorities aren’t yet familiar with the requirements for approving reused components. We’re the first to bring this approach forward, so they’re unsure what documentation and standards to ask for. We’ve been holding meetings with local authorities in Tampere to explain our processes and the documentation we provide. This helps reassure them that we’re following a rigorous process to ensure the safety and usability of these reused components.

Best of luck with your upcoming meetings. Now, as we wrap up, what impact do you hope this work package will have on the construction industry’s approach to reuse and sustainability?

Jukka: Our goal is to develop a process that’s robust but not overly burdensome. Striking this balance is crucial to encourage widespread adoption of reused materials in construction.

Lastly, what inspired you personally to focus on sustainable construction and the reuse of materials?

Jukka: My research career has centered on the durability of structures—how they degrade and what measures can prevent damage. At our university, we’re also focused on adapting construction practices to climate change. While some researchers study climate change directly, we’re more interested in its impact on the built environment. Reusing materials is an important part of this, as it allows us to avoid new resource extraction and reduce environmental impacts, contributing to a more sustainable future.