After four years of research and development on improving the bonding capabilities of synthetic ï¬bers, we recently patented a high-tensile-strength synthetic ï¬ber that partially ï¬brillates upon mixing and shooting, increasing its ï¬nal surface area and bonding capabilities to the concrete.1 The ï¬bers are introduced into the concrete mixer as monoï¬lament units of relatively low surface area (F4-a in Fig. 1), allowing up to 2% vol. (18.5 kg/m3 [31.2 lb/yd3]) ï¬ber dosages. During the mixing process, each ï¬ber transforms into a unit having several ï¬brils at its ends (F4-b in Fig. 1). The ï¬brils anchor each ï¬ber so their bonding capabilities are superior to those of