Properties of Fiber Reinforced Concrete: Workability, Behavior Under Long-Term Loading, and Air-Void Characteristics

This paper presents the results of an experimental invesigation of the behavior of steel fiber reinforced concrete. The properties investigated were: setting times, slump and air content loss with time, creep and shrinkage, and air-void characeristics including bubble size distribution. To compare the behavior of fiber reinforced concrete with plain concrete, all of the proceding properies were also investigated for plain concrete mixtures of similar composition. Two mixture proportions with cement contents of 611 and 799 lb/yd sup 3 (363 and 474 kg/m sup 3) were investigated. The lower cement content that was used with a water-cement ratio of 0.4 resulted in a highly workable medium-strength concrete. The compressive strength was in the range of 6000 psi (41 MPa). The higher cement content, wih a 0.3 water-cement ratio, resulted in a relatively stiff concrete with an average compressive strength of 7000 psi (48 MPa). High-range water reducers and air-entraining admixtures were used for all the mixtures. Collated 50 mm long steel fibers with hooked ends were used for the fiber concrete. The experiments were conducted using the appropriate ASTM standards. The air-void characteristics were studied using the linear traverse method. The results indicate that setting times are about the same for both concretes. Fiber concrete has lower slump and air content; the rate of loss of these parameters with time is also higher. Shrinkage of fiber reinforced concrete is slightly less, but it undergoes slightly more creep deformations. In the area of aid-void characteristics, the specific surface of air bubbles is lower for fiber reinforced concrete, and it has relatively less number of chord-intercepts in the 0 to 0.002-in. (0 to 0.05-mm) range.