A new building material developed at Empa is about to be launched on the market: "memory-steel" can not only be used to reinforce new, but also existing concrete structures. When the material is heated (one-time), prestressing occurs automatically. The Empa spin-off re-fer AG is now presenting the material with shape memory in a series of lectures.
So far, the steel reinforcements in concrete structures are mostly prestressed hydraulically. This re-quires ducts for guiding the tension cables, anchors for force transfer and oil-filled hydraulic jacks. The space requirements of all these apparatuses created the geometric framework conditions for every prestressed concrete structure; the strengthening of older structures therefore sometimes fails due to the high space requirements of this proven method.
In around 15 years of research work, experts from Empa and re-fer AG have now brought an alter-native method to series production readiness: shape memory alloys based on iron, which contract during heating and thus permanently prestress the concrete structure.
Hydraulic prestressing can thus be avoided - it is sufficient to heat the steel shortly, for example by means of electric current or infrared radiators. The new building material will be marketed immediately under the name "memory-steel". Several pilot projects, such as the reinforcement of various reinforced concrete slabs, have already been successful.
Development of memory-steel
The development of memory-steel began in the early 2000s. In the previous decades, Empa had al-ready pioneered the strengthening of concrete with carbon fibre reinforced polymers (CFRP). This led to the idea of using shape memory alloys for prestressing concrete.
Initial tests with nickel-titanium alloys were positive. However, the material known from medicine is far too expensive for use in the construction sector. In 2009, Empa researchers succeeded in developing an iron-based shape memory alloy, which they also patented. In 2012, researchers around Julien Michels finally founded the company re-fer AG; Michels has been CEO of the young company ever since.
New opportunities for old buildings
memory-steel should first of all be used for the strengthening of existing buildings. As soon as, for example, new windows, doors or lift shafts are installed in the concrete structure of an old building, a new reinforcement of the load-bearing structure is often unavoidable. In industrial buildings, the load-bearing capacity of an old suspended slab sometimes has to be increased.
Thanks to memory-steel, such tasks can now also be easily solved in confined spaces: Either a strip of special steel is fastened under the ceiling using dowels and then heated with electricity or an infrared radiator.
Alternatively, the reinforcement can also be set in concrete: First a groove is milled into the surface of the concrete slab, then a ribbed reinforcement bar made of memory-steel is inserted in-to the groove and filled with special mortar. Finally, the profile is heated with the aid of direct cur-rent and thus prestressed. Another variant is to embed the reinforcement bar in an additional shotcrete layer.
Precast concrete elements with special geometry
In the future, memory-steel could also be a proven method for manufacturing precast concrete parts with a previously unknown geometry. The hydraulic prestressing used up to now creates fric-tion in curved structures, which greatly limits the use of this method.
With a memory-steel profile embedded in concrete, highly curved constructions are now also possible: when heated, the profile contracts uniformly over its entire length without friction losses and transfers the stress to the concrete.
Market launch of memory-steel
The ready-to-install memory-steel profiles are manufactured by Voestalpine Böhler Edelstahl GmbH & Co KG in Austria. The company is also working with re-fer and Empa to further develop the composition of the alloy.
The new building material memory-steel will be presented to interested building experts and archi-tects during four technical seminars. Contact persons include experts from re-fer, Empa researchers, concrete experts from Sika AG and concrete profile manufacturer Stahlton AG.
Dates of the symposia
30 October 2018 Empa, Dübendorf - 13.15 h to 16.45 h
31 October 2018 Empa, St.Gallen - 13.15 h to 16.45 h
5 November 2018 FH Luzern - 13.15 h to 16.45 h
7 November 2018 Kursaal Bern - 13.15 h to 16.45 h
Dr. Christoph Czaderski
Empa, Structural Engineering
Tel.: +41 58 765 4216
Dr. Julien Michels
Tel.: +41 58 765 4339
voestalpine BÖHLER Edelstahl GmbH & Co KG
Tel.: +43 3862 203 60 62
J Michels, M Shahverdi, C Czaderski; Flexural strengthening of structural concrete with iron-based shape memory alloy strips; Structural Concrete (2018); DOI: 10.1002/suco.201700120
Rainer Klose | Empa - Eidgenössische Materialprüfungs- und Forschungsanstalt
Wood that Shapes Itself
16.09.2019 | Universität Stuttgart
For a better climate in the cities: Start-up develops maintenance-free, evergreen moss façades
25.06.2019 | Technische Universität Kaiserslautern
How long the battery of your phone or computer lasts depends on how many lithium ions can be stored in the battery's negative electrode material. If the battery runs out of these ions, it can't generate an electrical current to run a device and ultimately fails.
Materials with a higher lithium ion storage capacity are either too heavy or the wrong shape to replace graphite, the electrode material currently used in...
To process information, photons must interact. However, these tiny packets of light want nothing to do with each other, each passing by without altering the...
Researchers from the Department of Atomically Resolved Dynamics of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg, the University of Hamburg and the European Molecular Biology Laboratory (EMBL) outstation in the city have developed a new method to watch biomolecules at work. This method dramatically simplifies starting enzymatic reactions by mixing a cocktail of small amounts of liquids with protein crystals. Determination of the protein structures at different times after mixing can be assembled into a time-lapse sequence that shows the molecular foundations of biology.
The functions of biomolecules are determined by their motions and structural changes. Yet it is a formidable challenge to understand these dynamic motions.
At the International Symposium on Automotive Lighting 2019 (ISAL) in Darmstadt from September 23 to 25, 2019, the Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP, a provider of research and development services in the field of organic electronics, will present OLED light strips of any length with additional functionalities for the first time at booth no. 37.
Almost everyone is familiar with light strips for interior design. LED strips are available by the metre in DIY stores around the corner and are just as often...
Later during this century, around 2060, a paradigm shift in global energy consumption is expected: we will spend more energy for cooling than for heating....
19.09.2019 | Event News
10.09.2019 | Event News
04.09.2019 | Event News
20.09.2019 | Life Sciences
20.09.2019 | Life Sciences
20.09.2019 | Life Sciences