This paper presents the results of an extensive investigation to determine the behaviour and performance characteristics of the most commonly used fiber reinforced concretes (FRC) for potential airfield pavements and overlay applications. A comparative evaluation of static flexural strength is presented for concretes with and without four different types of fibers: hooked-end steel, straight steel, corrugated steel, and polypropylene. These fibers were tested in four different quantities (0.5, 1.0, 1.5, and 2.0% by volume), and the same basic mix proportions were used for all concretes. The test program included (a) fresh concrete properties, including slump, vebe time, inverted cone time, air content, unit weight and concrete temperature, and hardened concrete properties; (b) static flexural strength, including load-deflection curves, first-crack strength and toughness, toughness indexes, and post-crack load drop; and (c) pulse velocity. In general, placing and finishing concretes with less than 1% by volume for all fibers using laboratory-prepared test specimens was not difficult. However, the maximum quantity of hooked-end fibers that could be added without causing balling was limited to 1% by volume. Corrugated steel fibers (type C) performed the best in fresh concrete; even at higher fiber contents (2% by volume), there was no balling, bleeding, or segregation. Higher quantities (2% by volume) of straight steel fibers caused balling, and higher quantities of polypropylene fibers (2% by volume) entrapped a considerable amount of air. Compared with plain concrete, the addition of fibers increased the first-crack strength (15% to 90%), static flexural strength (15% to 129%), toughness index, post-crack load-carrying capacity, and energy absorption capacity. Compared with an equal 1% by volume basis, the hooked-end steel fiber contributed to the highest increase, and the straight steel fiber provided the least (but appreciable) increase in the above-mentioned properties.
Abstract