Behavior of soil-cement that has been modified by the addition of fiber reinforcing is investigated. Two different soil mixtures were used--one containing a sand aggregate and the other containing a clayey sand aggregate. Four different types of fibers were examined--straight steel, hooked steel, polypropylene, and fiberglass. All fiber mixtures were evaluated based on a comparison with a control mixture containing no fiber reinforcing. The material properties examined were: 1) compressive strength; 2) splitting tensile strength; 3) shear strength; 4) compressive stress-strain behavior; 5) wet-dry durability; and 6) freeze-thaw durability. Overall, fiberglass reinforcing was found to be most effective in improving the strength properties of the soil-cement. An increase in tensile splitting strength of up to 140 percent was observed. Ductility was greatly enhanced for all the fiber mixtures, as indicated by higher post-peak strengths. Also because of the presence of fibers, the confinement of specimens was improved. For some fiber/soil combinations, increases in compressive strength and shear strength were also observed. The wet-dry and freeze-thaw tests showed that all the fiber types except fiberglass improve the durability of soil-cement. Fiberglass fibers, however, were generally found to be detrimental to durability. In view of substantial increases observed in tensile splitting strength, ductility, durability, and confinement, it is suggested that fiber reinforced soil-cement might be applied in the construction of soil-cement liners for reservoirs and landfills.

Paper presents the results of an experimental investigation to determine the flexural fatigue strength of concrete reinforced with collated fibrillated polypropylene fibers. The performance of fresh concrete and the elastic and mechanical properties of hardened concrete are compared for concretes with and without fibers. The test program included 1) flexural fatigue and endurance limit; 2) static flexural strength including load-deflection curve, determination of first-crack load, and toughness index; 3) compressive strength; 4) static modulus; 5) pulse velocity; 6) unit weight, workability, and finishability of fresh concrete. The complete series of tests was run for three concentrations of fibers. Special care was taken to insure consistency with cement, aggregates, admixtures, procedure, and mix temperatures. There was no "balling" or tangling of the fibers during mixing and placing. Fiber reinforced concretes had better finishability and were easy to work with even at higher fiber concentrations. Due to the addition of fibers, the ductility and the post-crack energy absorption capacity was increased. There was a slight increase in the static flexural strength and a moderate increase in the flexural fatigue strength. When compared to plain concrete, there was a positive improvement in the endurance limit (for 2 million cycles).

Paper focuses on technological aspects of steel fiber reinforced concrete (SFRC) related to the workability improvement, unconventional compaction techniques, and low-pressure steam curing. Major research data are presented, along with suggestions for future applications of some of the techniques discussed.

Restrained shrinkage tests were carried out on ring specimens of concrete reinforced with polypropylene fibers. These fibers had a relatively improved modulus of elasticity and enhanced bond with portland cement matrix. To achieve uniform dispersion for the relatively high fiber content (2 percent volume fraction) employed, a conventional pan mixer was attached with a high-speed activator. It was observed that even after severe drying, no visible cracks (cracks wider than 0.01 mm) appeared on the polypropylene fiber reinforced specimen.

Results of an experimental investigation on the behavior of partially prestressed T-beams are presented. High-strength concrete with strengths higher than 8800 psi (60.6 MPa), mild steel with a yield strength of 60 ksi (413 MPa), 270 ksi (1,860 MPa) 7-wire strands, and 30-mm fibers with hooked ends were used for the entire investigation. Condensed silica fume and high-range water-reducing admixture were used to obtain the high-strength concrete. Six T-beams were tested using a simply supported span of 7 ft 6 in. (2286 mm) and two concentrated loads. The main variable was the fiber content that was varied from 0 to 250 lb/yd3 and (147.5 kg/m3). Only the minimum shear reinforcement (stirrups) was provided for all the beams. The flexural reinforcement was designed to create a shear failure to evaluate the fiber contribution to shear at low shear spans. The beams were instrumented to measure stresses in nonprestressed and prestressed reinforcement, curvature, crack spacing, crack width, and deflection. Companion cylinders were tested to obtain the compressive strength of concrete. Five out of six beams failed in shear mode. The fibers do contribute to the shear capacity. However, the contribution of fibers to shear is less for low shear spans, as compared to the contribution of fibers to shear capacity reported in the literature. The fiber reinforced concrete beams undergo more deformation before failure. The increases in fiber content result in consistent increase in flexural stiffness and cracking moment, decrease in crack spacing and maximum crack width, and reduction in reinforcement stresses and concrete strains.