Workability and Strength Properties of Steel Fiber Reinforced Concrete

Abstract

<p>The strength properties of fiber concrete have received much attention in the past with little emphasis being placed on the workability of the composite in its fresh state. Both field and laboratory studies have identified workability of the composite as a potential problem due to fiber addition resulting in field strengths lower than those obtained in the laboratory. Therefore, in addition to studying strength properties such as fatigue, the workability of fiber concrete was considered in detail.</p> <p>To obtain an optimum mix in terms of strength and workability, fiber length and concentration are of considerable importance. In the initial stages of the study, direct pull-out tests were completed to determine the optimum fiber length i.e. the fiber length just sufficient to allow full bond development under ideal conditions. The theoretical critical fiber length (1.8 cm) was found to correspond closely with the experimental optimum length of 1.27 to 1.91 cm.</p> <p>Emphasis was placed on the static and fatigue flexural strengths which are important properties required for rigid pavement design. Compression, split cylinder and impact resistance strengths were also considered. The tests indicated the importance of adequate workability with respect to obtaining improved strength performance with fiber addition. An increase in fiber length and/or concentration, decreased the workability of the composite resulting in an increased number of flaws decreased compaction and decreased uniformity of fiber distribution. The relative strength increase or decrease was dependent on the predominant influence; i.e. strength loss due to increased flaw generation or strength increase due to the fiber addition. The only significant factor influencing workability besides adjusting the fiber length and/or content was with the use of super-plasticizers.</p>