Fiber-reinforced concrete

Fiber-reinforced concrete is concrete, are the properties to improve its special fibers added. This leads, inter alia, to improve the tensile strength ( Nachrisszugfestigkeit ) and the ductility, and hence the breakage and cracking behavior. The most common applications are steel fiber concrete and glass fiber reinforced concrete (concrete with embedded glass fibers).

Properties

The embedded in the concrete fibers enter the building materials fiber concrete properties that differ from the concrete:

• During setting of the fiber concrete shrinkage cracks can be prevented
• The tensile strength can be increased
• With the increase of the tensile strength to increase the compressive strength
• At break results in a Nachrissfestigkeit
• The component can be subjected to bending

Depending on the base material and the shape of the fiber and its dosage, the properties can be controlled consciously within certain limits.

Fibers

Fibers are usually of three different base materials. These have very different properties in terms of density, deformation and strength. These properties are compared with a conventional concrete to the large differences can be seen in the following compilation also.

The following compilation shows these base materials, the sizes of conventional fibers and their moduli. Additionally there is a variation of the geometric shape usual.

Dosage

The amount of fibers per cubic meter of concrete is called dosage. This is critical for the properties of the fibrous concrete. The different fiber materials, the doses indicated in the illustration are common.

The measurement of the dosage of steel fiber concrete is now displayed in the book "Steel fiber reinforced concrete " by Bernhard Wietek Verlag Vieweg - Teubner 2008, in which case all the stresses are calculated. Thus, the steel fiber reinforced concrete can be applied to structural components, such as walls, pillars, beams and ceilings. In particular, the shear strength of this building material is compelling, since the load case punching is hardly decisive.

Use

The use of fiber reinforced concrete in structural members is regulated differently in different countries. The relevant building regulations must be observed. In Germany and Austria, for example, there is the directive fiber concrete. In Germany there are in addition to the approvals of various steel fiber manufacturer for components such as foundation slabs or basement walls in residential construction nor the DBV steel fiber concrete in October 2001., Where the use of the building material is transiently regulated. For industrial floors made ​​of steel fiber reinforced concrete are generally no building code restrictions, so that the product is used there most often. The tendency now is to jointless systems with field sizes up to 40 x 40 meters. In Switzerland, steel fiber shotcrete is often used to fuse in tunneling or excavation and slope protection. Recently, however, a movement has come in the application because the book of Wietek an assessment of structural components is possible. Applications in this regard have been carried out quite successfully with steel fiber concrete. The following table shows the different uses for each fiber raw materials from today's perspective are pointed out.

Regulations

There are no standards for fiber concrete available. Fiber concrete is governed, inter alia, the following guidelines:

• German Committee for Reinforced Concrete: Directive "Steel fiber reinforced concrete ", 2010.
• Leaflet steel fiber concrete of the DBV ( German Concrete Association )
• Directive fiber concrete of ÖVBB ( Austrian Society for Concrete and Construction Technology).
• Leaflet fiber modified concrete ( FMB ) - production, processing, Testing fresh concrete ( Professional Association fiber concrete eV)