Concrete with steel fibers


Steel fiber concrete is a relatively new type of concrete recipe that first appeared in the 1970s. The properties of the concrete thereby change considerably, but not always to the advantage. Although there are many uses for concrete with steel fibers depending on the lobby behind, using concrete with steel fibers is not uncontroversial.

Composition of steel fiber concrete

Steel fiber concrete is concrete enriched with steel fibers. The amount of steel fibers introduced per cubic meter of concrete is referred to by those skilled in the art as dosing. The steel fibers used have different fibers that are used:

  • Steel wire fibers wavy, profiled or smooth, each with end hook (anchor)
  • profiled or embossed chip fibers
  • profiled or embossed sheet metal fibers
  • milled steel fibers, sickle-shaped cross-section

dosage

For these steel fibers, the usual dosage for in-situ concrete is 20 to a maximum of 60 kg / m³, for shotcrete the dosage ranges from 30 to 80 kg / m³. However, especially with shotcrete, a high level of machine wear is to be expected, there is also the danger of hedgehog formation by the steel fibers. Basically, the corrosion of concrete with steel fibers is subordinate to other properties, but by no means negligible.

Cracks in concrete with steel fibers

In particular, the cracking already during processing (micro-stress cracks) up to the Nachrissausbildung are significantly influenced by the steel fibers. The microcracks (between aggregate and cement paste or cement stone) that are common in the curing of concrete are better stabilized. Likewise, the formation of shrinkage cracks is significantly lower.

However, with increasing steel fiber dosage, the pressure load characteristics change. These are high, but it is also a significant increase in the flexibility or the plastic deformability (ductility) to observe a concrete part. However, this is accompanied by a significant increase in the development of tears.

Positive properties of steel fiber concrete

Overall, the use of steel fibers has changed the following properties:

  • higher pressure resistance
  • higher abrasion resistance
  • higher plastic deformation (ductility)
  • a higher tensile strength
  • Due to the ductile behavior, the otherwise rather poor concrete properties during the tearing process change positively
  • improved thermal conduction properties

Use of this concrete

Basically, steel fiber reinforced concrete should not be used wherever cracks are troublesome, especially in the case of stress-bearing components. On the other hand, the concrete is much more elastic, without sacrificing compressive strength, but at the same time gains in tensile strength.

When building a house (building construction) to pay attention

Steel fiberbasons are still not covered by the standards in Germany. In particular, when building the house, therefore, the DIN 1045 applies without restriction. When used as a foundation or floor slab in house construction steel fiber reinforced concrete is controversial. In addition, there is a lack of legal certainty due to missing DIN standards. Should steel fibers be used to make strip foundations or load-bearing floorboards, this concrete should not be left unattended.

Combination of steel fibers and steel reinforcement

A combination of steel fibers and steel mesh or Moniereisen is urgently advised. In addition, there must be a corresponding building permit for concrete with steel fibers. As a rule, however, an exemption is granted by the individual examination. On the other hand, there are a few companies that use reinforced concrete methods, which are generally suitable for building.

Here the positive properties of steel fiber concrete are used

Consensus regarding the use of steel fiber reinforced concrete meanwhile exists with the following components:

  • Screed or concrete floors
  • industrial flooring
  • especially for heated floors (improved thermal conductivity compared to conventional concrete)
  • concrete roads
  • special precast concrete parts
  • Garage walls and foundation
  • shotcrete

In particular, as shotcrete, the positive properties are emphasized. House walls, but also rock walls can be secured without great effort with excellent values.

Tips & Tricks

Handyman will hardly be embarrassed to have to make components made of steel fiber concrete. However, especially home builders, so builders, necessarily inform. To mention here is that the contractor may not use steel fiber concrete without the written consent of the builder. However, in the case of property developers, it is usually not the future owner, but the developer, who is the client.


Video Board: Steel fiber concrete reinforcement – how does it work?