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