Technical Questions

ACI Committees, Membership, and Staff have answered common questions on a variety of concrete related topics.

What fibers are used in concrete?

Q. What fibers are used in concrete?


A. Short fibers produced from steel, glass, and organic polymers (“synthetic” fibers) are used to enhance the cracking-related properties of fiber-reinforced concrete (FRC). Naturally occurring vegetable fibers, such as sisal and jute, are also used. The enhanced properties may include reduced crack width, increased residual strength (ASTM C1399), fatigue life, resistance to impact, and fire resistance (ACI 544.1R). Synthetic fibers are used in small amounts (approximately 0.1% by volume of concrete) to reduce plastic shrinkage cracking. Synthetic and metal fibers are used in larger amounts (0.3% or more by volume) to improve flexural strength and toughness, and to control the crack width in hardened concrete (ACI 544.1R). The amount of fibers used will depend on the type and geometry of the fibers and the specified end use. Fibers reduce the workability of concrete, necessitating the use of water-reducing and high-range water-reducing admixtures. Use of fibers may require longer mixing times and must be added during a particular segment in the mixing process.


References: SP-1(02); ACI 544.1R; ACI 544.8R-16; ACI PRC-544.4-18; SP-81; SP-272; SP-280; ASTM C1399; SP-343; ACI PRC-215-21; ACI PRC-544.11-22

Topics in Concrete: Concrete Fundamentals; Fiber Reinforced Concrete; High Performance Concrete

Other Sources for Answers

Search other resources on the ACI website for answers to technical questions