So you are considering using steel fibers as a reinforcement – perhaps for an industrial concrete floor? An excellent idea, as steel fibers provide the properties you need such as high tensile strength, ductility, and toughness.
However, it is important to select the correct steel fiber for a specific application. This means understanding the differences between the two main types of steel fiber that are used for concrete reinforcement, namely Type I and Type II steel fibers.
Firstly, their similarities. Both types are usually used in diameters of 0.5-1.0 mm and lengths of 25-60 mm. Both are added to the concrete mix in a percentage range of 0.5% to 2.5% by volume. The main differences between the two types are their chemical composition and their resulting mechanical properties.
Type I steel fibers are made from low-carbon steel wires, while Type II steel fibers are made from high-carbon steel wires. This difference in composition results in different mechanical properties of the fibers and their suitability for different applications.
These fibers are typically used to increase the toughness and durability of concrete. The addition of Type I fibers increases the tensile strength of concrete, prevents crack propagation, and enhances the energy absorption capacity of concrete.
Type I fibers have a lower tensile strength than Type II fibers, but they have higher elongation and ductility. This makes them suitable for applications where crack propagation needs to be prevented, such as in concrete pavements and industrial floors.
Type II fibers are typically used to increase the flexural strength of concrete. They are also used to enhance the post-cracking behavior of concrete and to reduce the shrinkage and cracking of concrete due to drying.
Type II fibers have a higher tensile strength but lower elongation and ductility than Type I fibers. This makes them suitable for applications where the flexural strength of concrete needs to be increased, such as in precast concrete elements and structural members.
Dramix® steel fibers are typically classified as Type I steel fibers according to ASTM A820/A820M-16a. Dramix® are thus low-carbon steel fibers that are cold-drawn. But that’s not the whole story. In third-party testing, Dramix® outperforms Type II steel fibers even at lower dosage rates (over 200% better at 50 pcy).
This is interesting, because Type II steel fibers are commonly used for crack control (micro cracks). In such applications, Type II steel fibers are often used at very high dosage rates of up to 66 pcy. This makes the concrete slabs unnecessarily expensive.
Slabs reinforced with Dramix steel fibers are able to be optimized with different dosage rates and slab thicknesses because the fibers provide a post-crack flexural capacity in addition to crack control. Furthermore, the slab thickness and fiber dosage are calculated based upon engineering principles rather than just experience and the usage of plain concrete. This makes a Dramix® solution extremely cost-effective.
Millions and millions of square feet of concrete have been successfully reinforced with Dramix® Type I steel fibers around the world. They have a tensile strength of at least 70 ksi (480 MPa), and are commonly used in concrete applications to enhance the material’s strength, durability, and toughness properties – and provide outstanding crack control.
We hope you now see why it is important to select the correct steel fiber for your intended application to ensure optimal performance and durability of the reinforced concrete structure. At Bekaert our experts are always willing and available to give you specific recommendations and help you make the correct choice. Feel free to contact us with your questions about the correct steel fiber to choose for your specific application.