Fibers replace reinforcement – Rapid construction
with fiber-reinforced semi-precast elements

Installing conventional reinforcement is expensive and time-consuming. This process step is eliminated by using steel fiber reinforced concrete. However, in general, fibers are not used as the only structural reinforcement but in combination with conventional reinforcing steel bars because of the usually lower tensile capa-city. In case of very high fiber volume fractions and subsequently consolidating material behavior, steel fiber reinforced concrete is nevertheless able to absorb the structurally required load transfer without additional reinforcement [1]. Then, concrete should be placed in thin layers and in the precast concrete plant.

Steel fibers predominantly spread in two directions in slab-type structural elements so that semi-precast elements with supercritical fiber volume fraction of approx. 140 kg/m³ can replace a continuous reinforcing mesh. Semi-precast slabs having a thickness of 10 cm and an axial tensile strength of 3 N/mm² being verified experimentally exhibit the same calculated load-bearing capacity as reinforcement installed crosswise (fyk = 500 N/mm²) of approx. 6 cm²/m per direction.

The feasibility is experimentally demonstrated for centrally loaded footings with a geometry of l×b×h=1.1×1.1×0.3 m³. The semi-precast element made of steel fiber reinforced concrete serves as lower bending tensile reinforcement. A footing with reinforcing steel bars of Ø8-9 = 5.6 cm²/m per direction serves as reference. The steel fiber reinforced semi-precast footing achieves a load capacity of 1440 kN, while the reinforced concrete one features an approx. 175 kN lower capacity (Fig.). Verifications of the bending tensile force as well as the crack width control in accordance with DIN EN 1992-1-1 are fulfilled for both versions with nearly the same safety level. Thus, the footing made of semi-precast elements is an alternative to the conventionally reinforced footing. By omitting the production of a reinforcement cage and eliminating the subbase on site, a foundation made of semi-precast elements can be produced much faster, more resource-efficient and less expensive [2].

Related articles:

Issue 2017-02 New possible applications

High flexural tensile strength concrete

Nowadays, fiber-reinforced concrete is often used to increase the flexural tensile strength of the material. This approach enables a reduction in the ratio of conventional reinforcement or its...

Issue 2021-11 Monday, 15th November ? Innovation workshop (5)

MasterFiber: The sustainable and efficient reinforcement for precast concrete

MasterFiber structural polymeric fibers have been established for a long time ago in flooring and pavement applications replacing steel mesh or steel fibers. In recent years they have been used as...

Issue 2015-02 An alternative to conventional steel reinforcement?

Steel-fiber-reinforced concrete for lining segments

To an increasing extent, specifiers envisage the use of steel fibers instead of conventional steel reinforcement to resist tensile forces in lining segments of tunnels or large sewers. Particularly on...

Issue 2010-09 Overview of the Test Results

Innovative Precast Girders of Fiber and High-Performance Concretes

The stationary production processes offer precast construction optimal possibilities for applying high-performance concretes, for which remarkable developments have taken place (Fig. 1)....


New macro polymer fibers for load-bearing applications in concrete and sprayed concrete

With SikaFiber Force 50 and 60, Sika Deutschland GmbH launches two multitalented products as innovative concrete reinforcement. The high-performance polymer fibers produced in Germany are...