How can I guarantee that fibres will be distributed uniformly in the concrete?
The main parameter for the fibre distribution is the mixing time. Normally one (1) minute mixing time per m3 of concrete is required to ensure uniform fibre distribution. When the fibres are added directly into the truck mixer containing ready mixed concrete, the same rule applies. However the drum should rotate at full speed and the minimum mixing time should not be less then five (5) minutes. A second parameter that influences the uniform distribution is the aggregate grading. The sieve curve of the aggregates should be continuous and the maximum aggregate size should be adapted to accommodate the volume of fibres added. It should be noted that fibre distribution is considered uniform when all single dosage rate measurements based on a volume of ten (10) litres of fresh concrete do not deviate more then 20% from the targeted dosage rate.
