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How do fibers work?

Q. How do fibers work in concrete?

 

A. The fundamental mechanism by which fibers function in concrete is to provide post-crack tensile strength by bridging cracks that develop during loading or due to external factors. Since concrete is inherently weak in tension, fibers help arrest the propagation of micro-cracks, preventing them from growing into larger cracks. When a crack forms in the concrete matrix, intersecting fibers become engaged, resisting further opening or widening of the crack. This mechanism is known as "crack bridging."

 

The efficiency of fibers depends on several factors, including their material, geometry, orientation, distribution, and bond with the concrete matrix. The bond between fibers and the surrounding concrete is critical for stress transfer, enabling fibers to act as a secondary reinforcement system. This enhances the ductility, toughness, and crack resistance of the concrete, making it more resilient to external forces and environmental factors.

 

References: ACI 544.1R ACI 544.4R

Topics in Concrete: Concrete Fundamentals; Fiber Reinforced Concrete