Performance of dovetailed synthetic fibers in concrete

This research investigated the bond strength and toughness of a range of widely used commercially available synthetic Type 2 structural fibers defined within BS EN 14889 and compared these against novel prototype dovetailed (DT) synthetic Type 2 structural fibers. The DT shapes are three in number when viewed across the diameter of the circular DT fiber, and they run longitudinally, creating an open flute effect. Synthetic fibers tend to be made from low-modulus materials when compared with steel crack control products, and they suffer a greater diameter reduction and increase in length when compared with steel, for an equal load. Diameter reduction of fibers in concrete causes debonding and eventual failure. DT fibers are designed to offer additional bond when a diameter reduction occurs under load. Fibers were cast into concrete cubes to a depth of half their length and pulled out recording load and extension to ultimate failure. The findings showing large degrees of toughness were available when using DT fiber technology. The DT fibers transferred less bond stress at the point of the initial pull out prior to the DT feature of the fiber taking effect. The DT fiber under test provided additional grip through the contraction of the internal faces of the DT features when under load. Further work is needed to determine the optimum DT fiber diameter and aspect ratio that may provide increased bond stress while retaining large degrees of toughness.