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Q. What is the minimum fiber dosage? Is it possible to use less than the minimum dosage? A. The minimum fiber dosage in concrete depends on the application and type of fiber used. For synthetic microfibers, commonly used to control plastic shrinkage cracking in flatwork, the dosage ranges from 0.5 to 1.5 lb/yd³ (0.3 to 0.9 kg/m³) or 0.03 to 0.1 percent by volume for monofilaments, and at least 1.5 lb/yd³ (0.9 kg/m³) or 0.1 percent by volume for fibrillated fibers. In slab-on-ground applications, synthetic macrofibers require a minimum dosage of 3.0 lb/yd³ (1.8 kg/m³) or 0.2 percent by volume, while steel fibers typically require a minimum dosage of 15.0 to 20.0 lb/yd³ (9.0 to 12.0 kg/m³) or 0.11 to 0.15 percent by volume. Some structural applications, such as composite steel deck-slabs, may require higher minimum dosages. Using less than the minimum recommended dosage can result in insufficient fiber volume in the concrete mix, leading to performance similar to plain, unreinforced concrete rather than fiber-reinforced concrete. It is important to maintain the specified minimum dosage, even when using fibers with enhanced shapes, such as hooked, twisted, or embossed fibers. While these modifications can improve performance, they do not permit reductions in fiber dosage below the minimum threshold, as doing so can result in inconsistent or inadequate performance. References: ACI 544.1R, ACI 544.4R Topics in Concrete: Concrete Fundamentals, Fiber Reinforced Concrete
Q. What is the minimum fiber dosage? Is it possible to use less than the minimum dosage?
A. The minimum fiber dosage in concrete depends on the application and type of fiber used. For synthetic microfibers, commonly used to control plastic shrinkage cracking in flatwork, the dosage ranges from 0.5 to 1.5 lb/yd³ (0.3 to 0.9 kg/m³) or 0.03 to 0.1 percent by volume for monofilaments, and at least 1.5 lb/yd³ (0.9 kg/m³) or 0.1 percent by volume for fibrillated fibers. In slab-on-ground applications, synthetic macrofibers require a minimum dosage of 3.0 lb/yd³ (1.8 kg/m³) or 0.2 percent by volume, while steel fibers typically require a minimum dosage of 15.0 to 20.0 lb/yd³ (9.0 to 12.0 kg/m³) or 0.11 to 0.15 percent by volume. Some structural applications, such as composite steel deck-slabs, may require higher minimum dosages.
Using less than the minimum recommended dosage can result in insufficient fiber volume in the concrete mix, leading to performance similar to plain, unreinforced concrete rather than fiber-reinforced concrete. It is important to maintain the specified minimum dosage, even when using fibers with enhanced shapes, such as hooked, twisted, or embossed fibers. While these modifications can improve performance, they do not permit reductions in fiber dosage below the minimum threshold, as doing so can result in inconsistent or inadequate performance.
References: ACI 544.1R, ACI 544.4R
Topics in Concrete: Concrete Fundamentals, Fiber Reinforced Concrete