MADE POSSIBLE BY BETOLAMINA®-CAST: INTRICATE FACADES MADE WITH CONCRETE

Concrete is back in fashion as a construction material. It looks good, it’s versatile, and it offers excellent material properties, making it a popular all-rounder. It is also used for covering building envelopes, typically by adding “curtain wall” elements. On the other side, concrete is relatively heavy as a construction material due to integrated steel reinforcements and the required minimum concrete coverage to prevent corrosion. In partnership with FIBER-TECH Products from Chemnitz and Medicke Metallbau from Glauchau, the Steinbeis Innovation Center FiberCrete, also from Chemnitz, has developed a fiberglass-reinforced building concrete called BetoLamina®-Cast as part of a research project. The partners also developed a technology for producing and mounting thin-walled facades, simultaneously significantly reducing weight and achieving excellent visual properties. The Steinbeis Foundation honored the three project partners for their work with the 2019 Transfer Award.

There is demand for concrete that does not contain steel for use in modern curtain wall facades. Not only should these deliver the required mechanical qualities, they need to have thin walls, offer plenty of design options and deliver high-quality surfaces. This takes ingenious material concepts, innovative installation technology, and a reproducible production strategy. Strong demand for such solutions led Medicke Metallbau – an one-stop provider of premium-value building envelopes – to travel to Chemnitz to meet the Steinbeis Innovation Center FiberCrete and FIBER-TECH Products. The priority for their joint project was to map the overall process chain, from mixing the formula required for the concrete to logistical considerations and on-site installation.

The new fiber concrete, BetoLamina®- Cast, was first used in an office building called Wilhelm Kaiser Hof in Cologne, which required a “freeform” facade measuring approx. 5,000 sqm. The facade contains vertical elements at different angles (lesenes), which cast unexpected shadows that change continuously depending on the angle of light. All requirements were met for the facade in terms of the smooth surface, premium exposed concrete, a sophisticated matte appearance, weathering resistance, and robustness. Sharing insights from fundamental research at the Institute of Lightweight Structures at Chemnitz University of Technology with FiberCrete (the Steinbeis Innovation Center) offered the ideal vehicle for applying knowhow to this project. The Steinbeis Foundation Transfer Award – the Löhn Award was bestowed upon this project in acknowledgment of the close collaboration between the different partners and the successful transfer of research findings into practice.

“IT’S GOING TO BE EXCITING!”

An interview with associate Professor Dr. Sandra Gelbrich, Franziska Pfalz, and Marcus Medicke

Hello Dr. Gelbrich. When you think about intricate parts, concrete’s not exactly the first material you think of. You’ve done an impressive job in solving this apparent paradox. What makes your newly developed concrete so special?

Concrete is the world’s most widely used construction material. Its special properties allow it to meet a variety of visual, structural, and construction requirements in the long term. Concrete offers excellent compression qualities but comparatively poor tensile strength, so it generally has to be reinforced with steel. Steel tends to start corroding when it’s exposed to oxygen or moisture, so if it’s inserted in concrete, it needs to be protected. As a result, concrete measuring several centimeters has to be added to cover steel and ensure there’s a sufficient layer of alkaline in the concrete around the steel to shroud it from passive corrosion. But in turn, that means that concrete parts are solid and heavy and that raises resource requirements. So for a number of years now, people have been looking into steelfree reinforcement, for example by using alkaline-resistant glass and carbon fibers.

At the FiberCrete Steinbeis Innovation Center we’ve now developed a fiberglassreinforced building concrete called BetoLamina® for use as a facade component. It’s a new kind of white fiberglass concrete that offers excellent mechanical properties, outstanding durability, and magnificent visual qualities as an exposed concrete. BetoLamina®-Cast is a composition of five different materials, consisting of Portland cement, an aggregate with a maximum particle size of four millimeters, additives, a special admixture developed for the project, and alkaline-resistant glass fibers with a fiber length of 12 millimeters. This puts us in a position to create facade elements in complex shapes with a reproducible material thickness of two centimeters. We do this by producing a high-flow BetoLamina®-cast compound using particularly smooth formworks of fiberglass-reinforced plastics. We can also fulfill all kinds of design requests in terms of shape, surface structure, and color.

The products look excellent, they offer a variety of design options, and they deliver outstanding material properties, so our facade elements are in strong demand from architects and construction companies. Developing a new type of concrete is one thing in theory, but it’s another making components out of it in practice.

Ms. Pfalz: You took on this challenge at FIBERTECH Products. What requirements did you have to meet to do this?

Our know-how at FIBER-TECH lies in working on complex projects in the field of fiber composites. We solve structural requirements and transfer results into our products. The Wilhelm Kaiser Hof project in Cologne was the first joint project between FIBER-TECH, Medicke, and FiberCrete, and it was also the first facade for which FIBER-TECH had to produce 5,000 square meters of building concrete according to extremely high standards, so the project consortium faced one or two more challenges than usually to be expected.

Step by step, we set up a production and storage unit suitable for producing complete concrete elements, including an extra manufacturing area and special rooms, and we had to acquire and finance all of the required production equipment ourselves. In parallel to this, we hired extra people and trained them. To ensure we could produce 2,000 facade elements – that were reproducible in serial quality, without a hitch – we also had to set up a fully functioning, reasonably economical production line. To produce the elements in all the right shapes, we also developed our own mold-making technology, also to avoid high production costs. The success of the finished building facade shows that the investment, effort, and patience were worth it – all in a new area of business.

Mr. Medicke: Your team at Medicke was called in for its construction expertise – to look at the fixing elements for the facade, parts logistics, and last but not least actually installing the facade. What was your experience with the project and how has this now benefited you?

Modern facades require steel-free concrete that not only delivers the right mechanical properties but also has thin walls and can be used in all kinds of designs. It also has to offer excellent surface qualities. This requires clever material concepts, innovative fixing technology, and a reproducible production strategy. Lightweight construction and freeform design offer modern facade builders a whole host of new ways to design and construct complex building solutions.

The Kaiser Hof in Cologne was the first time – as a one-stop provider of building envelopes – that we’ve used this new kind of technology based on thin-walled concrete. We had a great deal of challenges to solve in terms of engineering, logistics, and installation. Making the BetoLamina®-Cast Fiberglass concrete element meant we had to develop a completely new kind of substructure and test it so it could be approved for construction purposes. From the very beginning, it was particularly important that the mounting brackets didn’t place unwanted stress on the fiberglass concrete elements and that they made them easy to attach without making mistakes.

To transport the 2,000m2 of fiberglass concrete elements, we had to build special mobile trestles to ensure they could be moved around the construction site safely without damage. The large number of elements – which each measured around 3.5 meters in length – also required an sophisticated loading and logistics system, which had to be available at just the right time for installation. The thin-walled fiberglass concrete elements required particularly careful handling while being installed on the building by our specially trained staff. This also entailed trying out new handling methods before the project, which were tested repeatedly to ensure installation was carried out as smoothly as possible. The planning and handling experience we gathered on this project has provided us with a solid foundation for using BetoLamina®-Cast fiberglass concrete in other projects in the future.

Ms. Gelbrich: You already know about the next big project your team will be implementing. Can you tell us briefly what the next collaborative project will involve for you?

I would describe using BetoLamina®- Cast on the new Wilhelm Kaiser Hof office building in Cologne as a remarkable success. We’re now carrying out ongoing developments to the product in keeping with market requirements. The projects we’re looking at include different surface structures, colors, shapes, construction techniques, and mounting technology. We’re also working on new technologies for the formwork and production of the elements. We’ve already started the facade on the German Institute for Standardization (DIN) building in Berlin. One particular challenge for us is composing a new kind of premium concrete mix and integrating designed glass particles in DIN blue on site, in a way that allows material content, optimized packing density, and fiber reinforcement to deliver the required mechanical properties yet still meet optical expectations in terms of the design and structure. It also has to be possible to process the new material mix using open casting and then finish the surface using sand-blasting. To select the right materials, we have to make sure the designed glass particles remain stable in the alkaline medium of the mineral matrix, and that they achieve the right density. It’s going to be exciting!