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Q. Why might fibers “ball up” in concrete mixes? A. Fiber clumping, or "balling," in concrete mixes is undesirable as it compromises the uniformity and strength of fiber-reinforced concrete. Clumping can occur due to the following reasons: Incorrect addition methods: Adding fibers too rapidly or in piles can lead to clumping, especially if introduced faster than the mixer can disperse them. Equipment issues: Rough loading chutes or worn-out mixing blades can contribute to fiber balling. Overloading: Using more than 2% fibers by volume, or more than 1% for high aspect ratio fibers, increases the likelihood of clumping. Inappropriate mix: Rapid addition to a non-fluid mixture or one with excessive coarse aggregate (above 55% by absolute volume) can cause clumping. Overmixing can also contribute. Inadequate dispersion: Uneven fiber distribution may require adjustments to batch size or mixing time. Inconsistent fibers: Variations in fiber length or geometry can lead to clumping. Lean concrete mixtures: Mixtures with low paste volumes are more prone to fiber balling. To prevent clumping, follow proper mixing procedures, ensure equipment is in good condition, and conduct pre-project test pours to verify the compatibility of the mix, fiber type, and dosage. References: ACI 544.1R, ACI 544.3R Topics in Concrete: Concrete Fundamentals, Fiber Reinforced Concrete
Q. Why might fibers “ball up” in concrete mixes?
A. Fiber clumping, or "balling," in concrete mixes is undesirable as it compromises the uniformity and strength of fiber-reinforced concrete. Clumping can occur due to the following reasons:
To prevent clumping, follow proper mixing procedures, ensure equipment is in good condition, and conduct pre-project test pours to verify the compatibility of the mix, fiber type, and dosage.
References: ACI 544.1R, ACI 544.3R
Topics in Concrete: Concrete Fundamentals, Fiber Reinforced Concrete