Jakob Fischer - Recreate

August 29, 2025

Jakob Fischer, Brandenburg University of Technology

The pilot project ‘Youth Centre at Sternentor’ in Hohenmölsen is entering the next important phase of the Recreate project. The construction project with dismantled and reusable concrete elements, initiated by the mayor Andy Haugk (town of Hohenmölsen, state of Saxony-Anhalt), designed by architect Christoph Henschel and scientifically supervised and managed by project leader Prof. Angelika Mettke (Department of Structural Recycling, BTU Cottbus Senftenberg), was put out to tender EU-wide for the project planning.

This article is intended to show that a tender with reusable reinforced concrete elements does not differ significantly from business-as-usual tendering procedures. This is a very important finding for the acceptance and spread of reuse projects in the future.

Introduction

The overarching aim of ReCreate is to realise a pilot project in each of the four partner countries (Finland, Germany, Sweden and the Netherlands), i.e. a building made from dismantled and reused concrete elements. Tasks such as acquiring the donor building, analysing the used concrete elements, logistics and transport of the elements, as well as planning the pilot project are implemented in an interdisciplinary manner in the four countries by the respective industrial partners and the scientific teams at the respective universities. This article describes one of the final steps for the German pilot project, which ultimately leads to the realised construction project. This involves the invitation to tender for the realisation of all planning and construction services in accordance with HOAI (Honorarordnung für Architekten und Ingenieure; translation: “Schedule of Services and Fees for Architects and Engineers).

During the course of ReCreate, several pre-drafts and a final design for the Hohenmölsen youth centre have already been created. HOAI-service phases 1-9:

1. basic evaluation

2. preliminary planning

3. design planning

4. approval planning

5. implementation planning

6. preparation of award of contract

7. participation in the award of contract

8. project supervision – construction supervision and documentation

9. project management

Together with the first structural parameters and calculations, both HOAI-service phase 1 (basic evaluation) and HOAI-service phase 2 (preliminary planning), could be completed through the ReCreate project. Accordingly, the tender for construction and planning services only had to be considered from HOAI-service phase 3 (design planning) and upwards.

However, before the tendering and awarding of planning and construction services could take place, the town of Hohenmölsen had to guarantee the financing of the youth centre. Through intensive application processes, the required investment sum of around €2.81 million was reserved via the Just Transition Fund (New European Bauhaus programme) in March 2025. However, before the final funding decision is issued, the complete design planning (service phase 3) must be submitted and it must be ensured that the entire construction project can be completed by mid-2027.

The funds from the ReCreate budget are not released as direct investments for the construction of the pilot projects; only construction and planning services that can be directly and exclusively justified by the additional costs of reuse could be financed via ReCreate.

Tender preparation

Once the funding through the JFT had been reserved, the law firm DAGEFÖRDE was commissioned to draw up the necessary tender documents in consultation with the town of Hohenmölsen and prepare them so that they could be published via an official tender platform (in this case: TED). Publication took place on 19^th June 2025 and was open to the public for 4 weeks until 18^th July 2025. The services were awarded as an EU-wide negotiated procedure with a call for competition in accordance with Section 119 (5) of the Act against Restraints of Competition (GWB – Gesetz gegen Wettbewerbsbeschränkungen) and Section 17 of the Public Procurement Ordinance (VgV – Vergabeverordnung).

The contents and special features of the tender documents – consisting of parts A to D – are described below with regard to reuse aspects. Episode 1 of this blog series explains the procedural conditions (Part A). The specifications (Part B) and the catalogue of questions for bidders in the tender documents will follow in Part 2.

Part A – Procedural Conditions

Part B – Project Specifications

Part C – Architects and engineer contract – Object planning services

Part D – Application for participation

Procedural Conditions (Part A)

Part A of the tender documents contains, among other things, information about the parties involved in the award process, general framework conditions, the procedure, as well as requirements and eligibility criteria for the participants in the competition. In the case of more than four participants, eligibility and Selection criteria were formulated, which will be explained in more detail later. If the participants fulfil the eligibility criteria, they are invited to submit offers and become bidders.

As mentioned at the beginning, the tender documents were available for public inspection and download for four weeks. In the first 21 days after publication, participants were able to submit objections, questions or even complaints regarding the content or form of the tender documents in the event of ambiguities or contradictions. This option was used several times and is included in the second part of this blog under ‘Bidder question catalogue’.

The award procedure described here is a so-called 2-stage award procedure. This means that there is first a phase with a public competition (the 4 weeks mentioned above) and then a bidding phase.

In the first phase, no tenders are submitted, only the Proof of Suitability (see next section). In the second phase, suitable participants and a maximum of four participants are invited by the procurer (City of Hohenmölsen) to submit an initial bid. If more than four participants have expressed an interest in the competition and fulfil the eligibility criteria, only the four participants with the highest scores will be invited to submit an initial bid in accordance with the selection criteria (see below). After submission of the initial bid, the city will invite the bidders to so-called bidder meetings (scheduled for week 36 this year).

Suitability Criteria

The seven suitability criteria to be established and fulfilled by the company or the bidding consortium comprise so-called self-declarations, two of which have been assigned with minimum requirements (*):

At this point, it is important to mention that only the planning with precast reinforced concrete elements had to be carried out for the suitability for the object planning, but not the reuse of these. However, reuse becomes relevant in the next step if more than four participants are selected.

Selection Criteria

If participants can fulfil the seven self-declarations including the two minimum requirements, they move on to the next round, the bidding phase. However, if more than four bidders have taken part and fulfil the suitability criteria, a selection procedure follows in which a maximum of 1000 points can be achieved. These are calculated by adding up the following four selection criteria:

The term ‘reuse’ mentioned under the selection criterion is defined in the tender documents as follows:

“ ’Reuse’ means the utilisation of dismantled precast reinforced concrete elements from a donor building for the construction of another/new building.”

This definition and mentioning of the term ‘reuse’ in the tender documents is of great importance, as it avoids ambiguities and subsequent misunderstandings even before participation or submission of a tender.

The scores resulting from the eligibility and selection criteria determine whether the four participants with the highest total score are invited to submit an initial bid. The participants now become bidders.

As soon as the four bidders have submitted their initial offer, the so-called bidder interviews take place. Bidders can still be excluded at this stage. Once the bidder interviews have been completed, the bidders still in the competition are asked to submit a final offer. These offers undergo a final evaluation in accordance with the published award criteria. In the end, one bidder becomes the contractor and is awarded the contract to provide the building services for the ‘New construction of the Sternentor youth and leisure centre’ project. The Architect and engineer contract for object planning services (Part C) can therefore be signed.

As soon as this decision has been made (probably at the beginning/mid-October 2025), this blog series will be continued here on our homepage. Episode 2 will be published in the early Autumn with the specifications and the catalogue of bidder questions.

by ReCreate project

November 22, 2024

Jakob Fischer, Brandenburg University of Technology

As Europe strives to meet its sustainability targets, the construction industry’s environmental impact is under increasing scrutiny. The sector is responsible for a significant portion of Europe’s resource consumption and waste generation. A key solution lies in evaluating building stock for its potential to contribute to circular economy practices, particularly through the reuse of construction materials like prefabricated concrete components. By reducing waste and conserving resources, this approach can help achieve the European Union’s (EU) climate and sustainability goals.

Europe’s Sustainability Goals and the Construction Industry

The European Union has committed to several ambitious targets, primarily through the Sustainable Development Goals (SDGs), including Goal 9 (Industry, Innovation, and Infrastructure), Goal 11 (Sustainable Cities and Communities), and Goal 13 (Climate Action). These goals promote building resilient infrastructure, reducing waste in urban environments, and taking urgent action on climate change.

In parallel, European policies such as the Circular Economy Package, the EU Waste Hierarchy, and the European Green Deal aim to curb resource extraction and promote material reuse. The building construction industry, as one of the largest consumers of resources and generators of waste, is central to these efforts. By recovering reusable concrete elements from existing structures, the sector can reduce its carbon footprint and contribute to Europe’s climate neutrality goal by 2050. The ReCreate project is developing numerous implementations to achieve these contribution goals.

Assessing Building Stock for Reuse

Evaluating building stock involves analyzing existing structures to identify materials that can be reused in new construction projects. This is especially important as Europe’s built environment contains vast amounts of materials, particularly concrete, that can be repurposed instead of discarded. The work package 1 of the ReCreate project is developing an analysis and mapping of existing precast concrete systems and elements.

Prefabricated concrete components, which are common in many buildings, offer substantial potential for reuse. These modular elements can be removed, inspected, and repurposed in new projects, reducing the need for energy-intensive production of new materials. Since concrete production is responsible for a large share of carbon emissions, reusing elements as a whole can significantly lower the environmental impact of the construction industry. Emission reductions of up to 98 % in comparison to virgin material prefabricated concrete elements, can be saved by reusing existing elements.

Urban Mining and the Circular Economy

Urban mining is a key element in transitioning towards a circular economy, where resources are reused rather than discarded. Buildings, especially those built in the mid-20th century, contain prefabricated concrete components that are still in good condition and suitable for reuse. Rather than allowing these materials to become waste, urban mining enables their recovery, helping reduce construction and demolition waste (C&DW).

C&DW represents nearly 40% of the total waste produced in the EU, underscoring the pressing need for robust waste management strategies. By reusing concrete elements as a whole the construction industry can contribute to a significant reduction in CO2 emissions. With concrete production accounting for up to 8% of global carbon emissions, any reduction in its demand has a meaningful impact on climate change mitigation.

Overcoming Challenges in Building Stock Evaluation

While the reuse of building components offers significant sustainability benefits, several challenges remain. On the one hand the structural and architectural integrity of reusable concrete elements have been testified and is being proven within the ReCereate project, however no market for reused elements has been developed yet, which could satisfy the demand of sustainable re-construction. Hence, the working packages 1 and 6 with the deliverable 6.2 will give an overview of the distribution and amount of defined elements in the existing building stock.

Another challenge is to evaluate the needed information for exact types of elements in existing buildings from national building stock databases. With the support of building owners (e.g. providing information on their building stock), reviewing literature and archives on construction/production activities in the past and assessing the current and future demolition rate, a more accurate assessment of the building stock will be investigated.

A centralized database tracking reusable materials across Europe could further enhance urban mining efforts. By cataloging the types, quantities, and conditions of reusable components, such a system would allow construction companies to plan projects more efficiently, ensuring that recovered materials are utilized effectively. Parts of these efforts will be achieved within ReCreate.

Conclusion

The systematic evaluation of building stock and the adoption of urban mining practices can contribute significantly to Europe’s sustainability efforts. Reusing materials like concrete supports SDG 9 by promoting resource-efficient infrastructure. It also aligns with SDG 11 by reducing urban waste and improving resource management, while contributing to SDG 13 by helping reduce the carbon emissions associated with new construction.

Achieving this requires collaboration between policymakers, industry professionals, and researchers. Governments can implement the regulatory frameworks and incentives needed to make reuse the norm, while construction professionals must adopt new approaches that prioritize resource recovery. Also building owners should be sensitized, to regularly evaluate their building stock, keeping track of their own ‘urban mine’ and step forward to interested planners and stakeholder in the construction industry with their upcoming potential of deconstructable and reusable concrete elements.

The future of Europe’s construction industry is circular, and evaluating building stock is a key step in realizing this transformation.

by ReCreate project

July 5, 2024

Project and industry partners involved:

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

IB Jähne: Peter Jähne, Milena Zollner

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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