Memory-steel makes for new material to strengthen buildings
by Staff Writers
Zurich, Switzerland (SPX) Oct 24, 2018
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
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
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 radi-ator.
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
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 con-crete.
Market launch of memory-steel
The new building material memory-steel will be presented to interested building experts and architects during four technical seminars. Contact persons include experts from re-fer, Empa research-ers, concrete experts from Sika AG and concrete profile manufacturer Stahlton AG.
Use of raw materials to double by 2060: OECD
Paris (AFP) Oct 22, 2018
Global use of raw materials is expected to double by 2060, "placing twice the pressure on the environment" than at present, according to an OECD study released on Monday. The study "sees global materials use rising to 167 gigatonnes in 2060 from 90 gigatonnes today," the Organisation for Economic Cooperation and Development, a group of advanced economies, said. It gave increases in population, economic activity and living standards around the world as key reasons for the rise, and underscored th ... read more
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