Q. What is the best method to use to introduce steel fibers to the mixing system?
Steel fibers are handled differently than synthetic fibers when introducing the fibers to the mixing system. First, the dosage range per cubic yard for steel fibers is 20-120 pounds. Whereas, the typical dosage range for synthetic fibers in 1 to 3 pounds per cubic yard. The other major distinction between steel and synthetic fibers is specific gravity, which will effect the weight or mass to volume ratio. The steel fibers have a specific gravity of 7.8 whereas the synthetic fibers fall within the range of 0.9 to 1.4.

To introduce steel fibers correctly they must be introduced at a constant/uniform rate while the drum is revolving at mixing speed. The steel fibers may be introduced along with the conventional ingredients as long as they are fed at a constant/uniform rate. The most successful approach is to add the steel fibers after the conventional concrete ingredients have been properly mixed. A conveyor is used to introduce the steel fibers to the drum while it is rotating at mixing speed. The steel fibers are placed on the conveyor belt in a uniform manner from a pre-weighed bag or box. It is important that the workforce responsible for introducing the steel fibers has amassed the appropriate number of pre-weighed bags or boxes based on the number of cubic yards of concrete in the drum before they commence feeding the fibers. This will eliminate the potential for introducing more or less than the proper quantity.

The drum should continue to rotate at mixing speed for approximately three (3) minutes after all of the steel fiber has been added to the drum.

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