BTU - Recreate

by ReCreate project

December 13, 2023

Christoph-Henschel-BTU-Reusing-precast-concrete-elements-challenges.png

Christoph Henschel, BTU

In conventional architectural projects, the use of the building and the design concept typically determine the dimensions of the structure. This means that the height of spaces, as well as the width and length of rooms, are defined by what will happen in them once they are built. Constraints on the size of a building are usually only imposed by limited budgets, the site and its context, or zoning laws. All of this changes drastically when reused precast concrete comes into play. Suddenly, the structure dictates the spatial dimensions, the grid size or the floor heights of the building design. This changes the design task for the architect and presents new challenges. In order to show that these challenges are also full of opportunities, the following text describes the design process for the German pilot project within the ReCreate project, a youth center for the town of Hohenmölsen.

The design task began with a detailed analysis of the elements that could be salvaged from the donor building. Specific types, dimensions and available quantities of exterior and interior walls and ceiling slabs were determined. Preliminary tests of the concrete strength and examination of the reinforcement properties ensured the suitability for reuse in advance. With this catalogue of elements as a starting point, the design process for the new building could begin – always with the goal of using as many reused elements and as little new material as possible.

Resource: BTU Cottbus Senftenberg

The mayor of Hohenmölsen drew up a rough room plan that served as the basis for the initial design. It included a multi-purpose room, a kitchen and dining hall, several smaller rooms for offices or after-school use, and some additional rooms such as restrooms, storage, and a technical room. With these requirements in mind, an initial building layout sketch was created with the goal of locating the various uses in customizable areas of the future building. Conditions such as the distance from the entrance, the proximity of certain rooms to each other, or the orientation to the east, west, or south to ensure the best lighting were taken into account.

This initial sketch was then superimposed on a grid of 2.4m by 3.6m – the maximum length of the ceiling slabs in the donor building. After a few attempts and several iterations of rotating certain rows in the grid by 90°, two initial building designs were created and presented to the town of Hohenmölsen.

Resource: BTU Cottbus Senftenberg

A special design decision was to use the former exterior walls not only as exterior walls but also as interior walls in the new building to show that the building was created from reused elements. This also allowed for interior windows between two rooms, which was an interesting way to visually connect separate rooms.

Resource: BTU Cottbus Senftenberg

The two initial building designs were presented by BTU at the town hall of Hohenmölsen and then discussed by the mayor with the town representatives. As a result of this discussion, BTU was asked to make a number of changes to the design in terms of size and use. This second design phase resulted in a combination of the two previous designs into one more detailed approach. In this design, it was already apparent that for the larger spaces, such as the dining room and multi-purpose room, the 3.6m ceiling spans were not sufficient, so new beams and columns were introduced to create wider spaces with double the span, resulting in a width of 7.2m. At this point, the method of showing reused elements in black lines and new material in red on the drawings was established. This allowed for a quicker overview of where reused elements would be located.

Resource: BTU Cottbus Senftenberg

During this design phase, the concept of multiple entrances to the building was developed, so that there is not just one main entrance, but several ways to approach the building, which can activate the building’s surroundings much better.

After another round of feedback from the town of Hohenmölsen, some minor changes were made and terrace roofs were added to the design. In this design, it is now possible to enter and exit the building from all four sides. This allows users to access the site from all sides. In this design, 47 used exterior walls, 7 used interior walls and 56 ceiling slabs are used.

Resource: BTU Cottbus Senftenberg

Some time passed and the town of Hohenmölsen contacted BTU again, stating that the original space plan was not sufficient and that more space was needed. With the experience from the previous designs, a new layout was developed. The new design introduced the idea of a functional block with all building services such as kitchen, toilets, storage, etc., to be placed in the center of the building. This allows all the other rooms where youth activities or office work will take place to receive natural light.

Resource: BTU Cottbus Senftenberg

The downside of this design was that it had a huge footprint of almost 700 m2 due to the increased space requirements. This led to the idea of arranging the spaces on two levels, creating a two-story building. The previous spatial configuration of a service core with a surrounding corridor and entrances on all four sides of the site was retained. Due to the peculiarities of the reused concrete elements and the limited grid size, it was decided that the upper floor would be accessed only by an exterior staircase to simplify the construction and avoid potential fire safety concerns.

Resource: BTU Cottbus Senftenberg

In this final design, 35 exterior walls, 25 interior walls and 103 floor slabs from the donor building will be reused, resulting in a net floor area of 505 m2 on the ground floor and 263 m2 on the upper floor. The new structural elements are initially planned to be new precast concrete elements such as columns and beams. New exterior and interior walls will be made of wood stud walls and ecological insulation such as wood fiber boards. For the facade, the reused exterior walls can be insulated with only 6 cm of wood fiber boards due to the low density concrete they are made of, while the reused interior walls, which will be positioned as new exterior walls, will require 14 cm of insulation. The façade will be a ventilated cladding of reused wood panels and reused corrugated metal, installed as available.

All in all, the design process was challenging, but also interestingly unusual, because the building elements determined many decisions that would otherwise have to be made by the architect or the client. Introducing new elements and rotating the grid in certain places allowed for some flexibility and gave just enough freedom to realize all the required uses in the building. The German ReCreate country cluster hopes to start construction of the youth center in late 2024 or early 2025.

Resource: BTU Cottbus Senftenberg

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by ReCreate project

November 10, 2023

Viktoria Arnold, researcher at BTU Cottbus – Senftenberg, Germany

The assessment of the sustainability of buildings has been increasing rapidly in recent years. This is not only related to the international goals of the United Nations, which are set out in Agenda 2030[1] and include global ecological, economic and socio-cultural aspects in the building sector (SDG 11[2], 12[3] and 13[4]). It is also linked not only, but in large part, to the national goals of the United Nations, which each country has set for itself. Germany, for example, has set a goal of achieving greenhouse gas neutrality in its building stock by 2050[5]. Different countries have different requirement methods. Some countries have made it mandatory to submit a so-called Climate Declaration for future building during the approval phase and to comply with certain limits for greenhouse gas emissions, such as the Netherlands, Sweden and Finland. Other countries, such as Germany, subsidise climate-friendly construction and renovation measures. Some builder-owners are just interested in building sustainably and climate-friendly and want to know what design decisions, building products and materials have what impact on the environment. And what contribution the building as a whole makes to resource and climate protection during its entire life cycle. To find this out, many sustainability assessment systems for buildings are used, which have LCA (Life Cycle Assessment) as one of the most important criteria. The basis for LCA is the EPDs (Environmental Product Declarations) based on ISO 14025 and EN 15804 for the different building products and materials. The more building products and materials have an EPD, the more accurate the calculation of the environmental impact of a building. This will greatly assist the builder-owner when deciding on certain construction and architectural solutions, and what contribution the building as a whole makes to resource and climate protection throughout its complete life cycle.

I am doing my doctorate at BTU on sustainability assessment of single-family houses. For such buildings, which are nowadays a luxury from a climatic point of view, such an assessment is particularly important.

In the ReCreate project, our German Cluster is particularly responsible for work package 6 “Energy and Climate”, which aims to evaluate the environmental and economic impacts (LCA and LCC (Life Cycle Costing)) of the reuse of precast concrete elements. Our major objective is to produce one or more EPDs for the precast concrete elements (ceiling, exterior and interior wall) suitable for reuse. This will enable LCA for new buildings with the reused elements and distinguish such resource and climate-friendly projects from others. Several previous research projects led by Prof. Angelika Mettke[6] have shown that the reuse of concrete building elements can significantly reduce the carbon footprint and energy consumption in the product phase by up to 93-98% compared to new production[7].

We notice again and again in our research that reuse can only be possible if the parts are still considered in the installed condition and the careful disassembly is carried out by an experienced company in the best case. Recently, the new DIN SPEC 91484[8] has been published, which is the basis for evaluating the high-quality connection potential for building products before demolition and renovation works where Prof. Mettke has been involved. Another prerequisite for successful reuse is that the building documents are available and, if possible, up to date. This is rarely the case with existing industrially constructed buildings that are up for deconstruction. That is why today’s initiative on the building resource passport is very important, where all building materials and products used, as well as their quality and recyclability, are recorded and kept up to date. It is also important to look now at what can be used to build more sustainable buildings so that the new building can be reused later at the end of its life cycle.

I am asking all these research questions in my doctoral thesis because it is still not so far that one comes to the idea of building a single-family house from used precast concrete elements.

[1] Sustainable Development Goals

[2] SDG 11 Make cities inclusive, safe, resilient and sustainable

[3] SDG 12 Ensure sustainable consumption and production patterns

[4] SDG 13 Take urgent action to combat climate change and its impacts

[5] Deutsche Nachhaltigkeitsstrategie Weiterentwicklung 2021, p. 103

[6] Structural Recycling Unit, Faculty 2 of Environment and Natural Sciences, BTU Cottbus – Senftenberg

[7] Mettke, A. (2010). Material- und Produktrecycling – am Beispiel von Plattenbauten. Zusammenfassende Arbeit von 66 eigenen Veröffentlichungen, Cottbus, Techn. Univ., Habil.-Schr. p. 235–243

[8] DIN SPEC 91484:2023-09 “Procedures for recording building products as a basis for evaluations of connection use potential prior to demolition and renovation work.”

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by ReCreate project

January 11, 2023

ReCreate German Country Cluster leader Prof. Angelika Mettke was interviewed for an article in the regional daily newspaper Lausitzer Rundschau and for an online report of the ARD Tagesschau, in which she presented an already realized reuse project in Kolkwitz as well as the plans for the ReCreate research project. In addition to Prof. Mettke, the deconstruction company ECOSOIL (industrial partner in the German ReCreate Cluster) was also interviewed for the newspaper article. The title “Lausitz gives new life to old slabs” refers to the Lausitz region, where Cottbus is located and the BTU and ECOSOIL are based.

Both articles first present the sports clubhouse in Kolkwitz near Cottbus. In 2009, the building project was realized using used concrete elements. The used concrete elements were recovered from a prefabricated slab building from GDR times that was located in Cottbus. ECOSOIL was commissioned with both the deconstruction of the 8-story slab building and the construction of the new building. Prof. Mettke from BTU designed the construction project together with the future users and accompanied the implementation of the project scientifically with her team of employees. Based on the process recordings for the deconstruction and the reuse of the concrete elements, the savings in resources and greenhouse potential were calculated in comparison to a conventional design.

The (re)construction project serves the BTU and ECOSOIL as a reference for an implementation possibility and what is feasible, with concrete elements suitable for reuse. ECOSOIL has become the market leader in the careful element-oriented deconstruction of prefabricated buildings, while the BTU has become an initiator and consultation partner for (re-) construction projects.

In addition, Prof. Mettke and Axel Bretfeld (Managing Director of ECOSOIL) presented the ReCreate project and the European partnerships with the Finnish, Swedish and Dutch clusters. The goals and tasks of the project were outlined in the articles as well as an outlook on the planned German pilot project of a youth center in the city of Hohenmölsen.

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by ReCreate project

September 21, 2022

At the end of the summer, members of the German ReCreate cluster met with members of the Dutch cluster for a transnational technical exchange at a deconstruction site in the small town of Weißenfels near Leipzig in Germany. In consultation with the BTU project manager Angelika Mettke and the German industry project partner Dietmar Gottschling of ECOSOIL, the meeting was prepared on-site to show how partial dismantling is carried out under practical conditions.

The dismantling process was observed by Viktoria Arnold (BTU), Thijs Lambrects, Hamidullah Attaullah (both TU/e) as well as an employee of the office of Patrick Teuffel (head of WP5) at the location site, Hardenbergstr. 39-42. The demonstration allowed them the ability to gain an insight into the dismantling process directly on site.

Considering the process, the partial deconstruction comprised the top two floors of the 5-story prefabricated building of the “P-Halle” type, which was constructed from the same range of prefab elements as the donor building for the ReCreate German pilot project at Otto-Nuschke-Str. 9-14 in Hohenmölsen. Accordingly, the same range of slabs and panels had to be dismantled and the same connections opened. That resulted in 30 dismantled floor slabs which required transport from Weißenfels to Hohenmölsen, where the temporary storage site is located.

The dismantled floor slabs are planned to be (re)used later on the same site in the planned pilot project, the construction of a youth center. Concerning the remaining dismantled concrete elements, they had to be handled with more caution because of potential causes of material composition. By that means, they first had to undergo the process of pre-shredding at the dismantling construction site and then sent to a recycling plant for material processing.

Check out the pictures of the site below of the dismantling process at the deconstruction site:

ReCreate

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by ReCreate project

April 14, 2022

On the 7th of April, the ReCreate team of the AG Constructional Recycling of the BTU Cottbus met with the project partners at the location of the potential donor building Otto-Nuschke-Str. 9-14 (see photo 1) in Hohenmölsen for the 3rd German country cluster meeting, where Mr. Gottschling (Ecosoil GmbH) and the architect Mr. Dreetz were present as project partners.

ReCreate 1 — Photo 1 – the potential donor building Otto-Nuschke-Str. 9-14

Additionally, the mayor of the small-town Mr. Haugk and the chairman of WoBau Hohenmölsen GmbH (owner of the potential donor building) Mr. Luckanus also attended the meeting. After a discussion in the town hall on the possible realization of a (re)construction project with the used concrete elements and on the organization of the deconstruction itself, a possible building site (see photo 2) and the deconstruction object (donor building) in Otto-Nuschke-Str. were visited. On April 19, the gutting of the upper two floors of the residential building will begin and the scaffolding will be erected. From May 2 onwards, the partial deconstruction will be carried out by the company Ecosoil GmbH.

ReCreate 2 — Photo 2 – possible building site

The BTU research team has begun to examine the condition of selected concrete elements intended for reuse in the installed position. In addition to geometric construction surveys, concrete compressive strength measurements were carried out using rebound hammers (see photo 3). The purpose of this is to evaluate the structural condition of the concrete elements, which are about 40 years old, so they’ll be able to make a statement on their reuse within the scope of the suitability test. The technical measurement investigations will be continued in April along with the involvement of students and finally, the concrete elements suitable for reuse will be marked.

ReCreate 3 — Photo 3 – using rebound hammers for compressive strength measurements of concrete

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