Concrete experts have developed a new building material Memory-steel that can be used to reinforce new as well as existing concrete structures. In the construction of concrete structures, steel reinforcements are generally prestressed hydraulically which requires oil-filed hydraulic jacks, anchors for force transfer, and ducts to guide the tension cables.
These apparatus need specific spaces which created the geometric framework conditions for every prestressed concrete structures. The proven method, however, prevents reinforcement of older structures due to large space requirements.
Following 15 years of research work, concrete experts from Empa and re-fer AG have now developed iron-based shape memory alloys which contract on heating and permanently prestress the concrete structure, thus eliminating the need for hydraulic prestressing. According to the experts, steel can be sufficiently heated in short time period by means of either infrared radiators or electric current.
The new building material is expected to be marketed immediately as ‘memory-steel’. It has also been proven successful in various pilot projects such as strengthening of reinforced concrete slabs.
Development of the New Building Material
It started back in early 2000s, though Empa had already introduced concrete strengthening with carbon fiber reinforced polymers (CFRP) in the previous decade. This had influenced the experts to use shape memory alloys such as nickel-titanium alloys for prestressing concrete which showed positive results in the initial tests.
However, these alloys were too expensive to use in construction sector. After continuous research and tests, in 2009, researchers at Empa successfully developed shape memory alloy based on iron, which they patented.
In 2012, one of the researchers, Julien Michels founded the company re-fer AG who has been the CEO ever since.
New Opportunities for Old Concrete Structures
According to the researchers, the newly developed material should initially be used for the strengthening of old buildings. When new doors, windows, or lift shafts are installed in the concrete structure of an existing building, it becomes difficult to avoid the new reinforcement of the load-bearing structure.
Suspended concrete slabs in most of the industrial building are required to increase the load-bearing capacity which can be achieved by the memory-steel. It is operational even in confined space, for example, a strip of steel can be fastened under the ceiling using dowels and then heated with infrared radiator or electricity.
Future Prospects of Memory-steel
The concrete experts explained that memory-steel could also be a proven method for developing precast concrete parts with previously unknown geometric framework. It will further enable highly curved construction as the memory-steel profile, under heat, contracts uniformly over its entire length and transfer stress to the concrete without losing friction.