A brief summary of the main differences between Type I and Type II steel fiber

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.

Type I steel fibers are made from high-carbon steel wires, while Type II steel fibers are made from low-carbon steel wires. This difference in composition results in different mechanical properties of the fibers and their suitability for different applications.

Type I steel fibers are also cold-drawn per ASTM A820 while Type II steel fibers are manufactured as slit-sheets (cut into strips from thin steel sheets). This difference in manufacturing provides Type I steel fibers with a circular cross-section and Type II steel fibers with a rectangular cross section.

When to use Type I steel fibers

Type I steel fibers are typically used to increase the post-crack flexural strength of concrete but can also be used to replace temperature and shrinkage steel as well as to extend or eliminate control joints. 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 I steel fibers also have a higher tensile strength than Type II fibers and typically have hooked ends for anchorage into the concrete. This makes them suitable for applications where the reinforced concrete is preferred, such as in precast concrete elements and structural members in addition to heavily loaded industrial floors, mat foundations, and structured slabs spanning rigid inclusion elements.

When to use Type II steel fibers

Type II steel fibers are typically used to increase the crack control of concrete or to extend control joint spacing. The addition of Type II fibers prevents crack propagation, and enhances the energy absorption capacity of concrete. However, the design of the section is often done without considering any increased strength from these fibers. 

Type II fibers have a lower tensile strength than Type I fibers and weakened anchorage so they typically are not used to increase the flexural strength in concrete or in structural applications. This makes them suitable for applications where crack propagation needs to be prevented, such as in lightly loaded concrete pavements and industrial floors.

Is Dramix® a Type I or Type II steel fiber?

Dramix® steel fibers are typically classified as Type I steel fibers according to ASTM A820/A820M-16a. Dramix® are thus high-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 as the slab can often be thinner than when designed as plain concrete – saving cost and CO2 emissions in the process.

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 170 ksi and are commonly used in concrete applications to enhance the material’s strength, durability, and toughness properties – while providing outstanding crack control.

We can help you make the correct choice

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.