Material characterization: How SFRC differs from conventional reinforced concrete

Traditional reinforced concrete consists of concrete for compression and rebar for tension, each tested and classified independently:

• Rebar per EN ISO 15630‑1
• Concrete per EN 206

With these defined material properties, designers can evaluate sectional behaviour.

SFRC is fundamentally different.

It is a composite material whose structural performance cannot be derived from the concrete mix and fiber properties alone. Fiber–matrix interaction governs the post‑crack response, so the composite must be tested directly.

Standardized tests include:

• Steel fibers for concrete : EN 14889-1 (= material standard)
• Test method for steel fiber concrete:  (= test standard)

               - EN 14651  (Beam test)

               - EN 14488‑5:2006 (plate test)

               - ASTM 1609 (beam test)

               - ASTM C1550 (round panel test)

These bending tests characterize the post‑crack residual capacity, from which a stress–strain curve of the composite SFRC is generated. This curve forms the basis for structural design.

Alternatively, the energy absorption is derived from the test.

From composite behaviour to section design

Section design in conventional RC is straightforward: combine tensile force in the rebar, compressive force in the concrete, and the corresponding lever arm to obtain the moment resistance.

The same principles apply to SFRC, but with one important difference:

• Instead of a rebar force, the tensile stress block is derived from the standardized SFRC stress–strain curve.
• Combined with the concrete compression block, this yields the moment resistance of the SFRC section.

Thus, design is analogous to RC but based on composite tensile behaviour rather than discrete reinforcing bars.

From section design to structural design

A frequent misconception is that small‑scale bending samples cannot represent full structural behaviour.

This is precisely why design standards exist.

When designers work within a coherent standard family (such as EN), there is explicit alignment between:

• Material testing methods
• Partial safety factors
• Structural design provisions

In SFRC:

• Material factors account for the variability and scale of the test specimens.
• Design provisions include size‑effect corrections to translate small‑sample data to structural dimensions.

Following the normative framework ensures reliable ULS and SLS performance and supports safe, cost‑efficient design.

The role of large‑scale testing

Large‑scale testing is not intended to replace standardized small‑scale material tests.

Its primary role is to:

• Validate design models
• Confirm the coherence of the testing standards
• Support calibration of partial factors

Once validated, routine design should rely on the established standards. Maintaining consistency within this framework is the designer’s responsibility.