Types of concrete fibres: steel, synthetic, glass and basalt compared

Fibre reinforced concrete is a collective term for concrete containing steel fibres, synthetic fibres, glass fibres, basalt fibres, or combinations thereof. Each fibre type has its own profile in terms of strength, workability, cost and area of application. This overview helps you make the right choice — with references to the in-depth articles on each fibre type.

Steel fibres

Steel fibre reinforced concrete (SFRC) is made by adding roughly 0.3 to 1 volume percent of steel fibres to the concrete mix. Steel fibres allow the concrete to absorb tensile forces and carry heavier loads — in many applications they can partially or fully replace traditional reinforcement. SFRC structures have stronger corners and edges, higher abrasion resistance, and are more resistant to spalling from impact. Applications: industrial floors, assembly halls, bus shelters and road renovations.

Synthetic fibres

Within synthetic fibres, polypropylene is the most widely used material. These fibres are thin and usually 10 to 20 mm long, and are added in relatively large quantities (typically between 500 and 1,800 grams per m³ of concrete). Adding polypropylene fibres can achieve a range of effects, strongly dependent on the diameter, length, surface structure and shape of the fibre (single monofilament or fibrillated mesh). Synthetic fibres are particularly effective against early-age shrinkage cracks and, unlike steel, are not corrosive.

Glass fibres

Coated micro glass fibres give concrete a considerably higher splitting tensile strength than unreinforced concrete. Cast-in-place glass fibre concrete is still very much under development and is currently used mainly in yard paving. Glass fibre is an interesting option where high tensile strength and a non-corrosive property matter, but its application in the Netherlands is less widespread than steel or synthetic fibres.

Basalt fibres

The newest addition to the range: basalt fibre, extracted from molten volcanic rock. Basalt fibre combines a high tensile strength (3,000-4,000 MPa) with a low density (~2.7 g/cm³, almost three times lighter than steel), excellent heat resistance (up to ~700°C) and full recyclability. Applications include industrial floors, underwater concrete, sprayed concrete and tunnel structures.

Combinations: hybrid fibre solutions

In practice, fibre types are also combined. A combination of steel fibres with synthetic fibres, for example, offers the strength of steel for dynamic and mechanical loading, complemented by the shrinkage crack control of synthetic fibre. This kind of hybrid solution is used, among other things, for heavy, dynamically loaded structures.

Which fibre type suits your project?

The key strength and typical application per fibre type in one overview:

• Steel — high structural strength and abrasion resistance; typical application: industrial floors, assembly halls and road renovations.

• Synthetic (PP) — shrinkage crack control and non-corrosive; typical application: floors, foundations and sub-floors.

• Glass — high splitting tensile strength; typical application: yard paving (under development).

• Basalt — heat resistance, low weight and recyclable; typical application: industrial floors, tunnels and sprayed concrete.

In conclusion

There is no "best" concrete fibre in general terms — the right choice depends on the load, the desired properties and the application. In the following articles in this series we look in more depth at the properties, dosage and practical experience per fibre type.