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Q. How do you mix fibers into concrete? A. To optimize the performance of fiber-reinforced concrete (FRC), fibers must be uniformly dispersed throughout the concrete mixture. This may require adjustments to the batch size or an increase in the mixing time. While the fiber manufacturer’s recommendations should always be followed, the following general guidelines apply: For mixing in a transit mixer, fibers should be added to the rotating drum continuously after all other concrete ingredients have been added. A mixing speed of 10 to 12 rpm is typically used during fiber addition. Once all fibers are in the mixer, the concrete should be mixed for at least 40 drum revolutions, approximately 4 to 5 minutes, to ensure proper mixing and fiber dispersion. When using a central mixer, the mixing time and revolution rate are similar to those for plain concrete because the central mixer provides sufficient shear to achieve adequate fiber dispersion. Adjustments to batch size or mixing time may be necessary to ensure uniform fiber distribution. References: ACI 544.1R, ACI PRC-544.2, ACI PRC-544.3 Topics in Concrete: Concrete Fundamentals, Fiber Reinforced Concrete
Q. How do you mix fibers into concrete?
A. To optimize the performance of fiber-reinforced concrete (FRC), fibers must be uniformly dispersed throughout the concrete mixture. This may require adjustments to the batch size or an increase in the mixing time. While the fiber manufacturer’s recommendations should always be followed, the following general guidelines apply:
For mixing in a transit mixer, fibers should be added to the rotating drum continuously after all other concrete ingredients have been added. A mixing speed of 10 to 12 rpm is typically used during fiber addition. Once all fibers are in the mixer, the concrete should be mixed for at least 40 drum revolutions, approximately 4 to 5 minutes, to ensure proper mixing and fiber dispersion.
When using a central mixer, the mixing time and revolution rate are similar to those for plain concrete because the central mixer provides sufficient shear to achieve adequate fiber dispersion. Adjustments to batch size or mixing time may be necessary to ensure uniform fiber distribution.
References: ACI 544.1R, ACI PRC-544.2, ACI PRC-544.3
Topics in Concrete: Concrete Fundamentals, Fiber Reinforced Concrete