What is dry fiber balling?
Dry fiber balling is the most common form formed when fibers are admixed. The fibers are not sufficiently integrated into the matrix, resulting in fiber bundles that are covered with cement paste.
The rotation of the mixing drum then produces balls with a diameter of up to 150 mm. With the same slenderness, the fiber shape or design determines the tendency or potential for hedgehog formation. Typically, the risk of fiber balling increases with increasing slenderness (length-to-diameter ratio).
For the straight and high-strength steel fibers from STABILS, this rule applies only to a limited extent, because the steel fibers made from cold-rolled strip have micro-anchors and reduce the tendency to form hedgehogs due to their material properties.
What is wet fiber balling?
When mixing concrete, wet fiber balling can occur if the mixing time is too long, if the aggregate fails or if the maximum aggregate size is too large. It also occurs with segregation. Wet fiber balling occur after the fibers have already been distributed in the concrete and therefore contain mixed concrete with aggregates of any size. The use of bonded fibers is no guarantee against the formation of wet fiber balling.
