Investigation of Five Synthetic Fibers as Potential Replacements of Steel Fibers in Ultrahigh-Performance Concrete

Abstract

Ultrahigh-performance concrete (UHPC) has been considered for a variety of structural engineering applications, owing to its superior strength and durability. Among the main properties of UHPC, flexural performance characteristics largely depend on the type and dosage of fibers incorporated into the mixture. Noting this critical aspect and the fact that the availability and cost of fibers directly contribute to choosing UHPC over other cementitious composites, this study explored the possibility of a partial replacement of steel fibers conventionally used in UHPC mixtures with synthetic fibers. With a focus on workability and strength properties, a total of 15 mixture designs were developed, investigating five different synthetic fibers, including nylon, polypropylene, polyvinyl alcohol, alkali-resistant glass, and carbon fibers. Three mixtures were prepared for each fiber type by varying the dosages of synthetic and steel fibers. From the conducted tests, load-deflection curves were extracted, further to flexural strength and toughness characteristics. To properly understand the progress of crack formation and propagation, as well as the effectiveness of various fibers in the postcracking response of UHPC, the obtained results were paired with digital image correlation data. Through holistic comparisons, the outcome of the presented study provided original information on the extent of contribution of some of the most common synthetic fibers to the strain distribution, crack resistance, and flexural performance of UHPC.