International Concrete Abstracts Portal

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).

By lightening the weight of the building material, the vertical load can be decreased. This minimizes the quantity of material required for earthquake resistance. Furthermore, it increases on-site productivity. The objective of this study is to develop lightweight, durable L-FRC, and to apply it to the exterior walls of buildings. Structural design demands many performance specifications for the exterior walls--specific gravity, panel weight, flexural strength for maximum wind pressure, fireproofing, drying shrinkage, and freeze-thaw durability. The physical properties of L-FRC are produced by calcium-silicate-slag-type low alkaline cement, anti-alkali glass fiber, and a special chemical admixture that includes a superplasticizer, foaming agent, and other additives. The physical characteristics of L-FRC are obtained from laboratory tests, actual-size experiments, and construction work using L-FRC. The main results are: 1) The specific gravity is nearly 1.28, and the unit weight of the panel is 115 kg/mý (1.13 kN/mý) (7 days); 2) The flexural strength of specimens is 12.8 MPa (14 days) and that of full-scale panels is 8.80 MPa (28 days); 3) The compressive strength is 21.6 MPa (14 days); 4) L-FRC is officially recognized as a fireproof material; 5) The rate of drying shrinkage is less than 5 x 10-4 (180 days); 6) The durability factor is more than 90 percent. The physical characteristics of L-FRC were sufficiently greater than the specified standards for these characteristics. Therefore, exterior wall work can be satisfactory and successfully completed in a shorter period.

Calcium silicates (C4A3S-CS) slag-type low-alkaline cement (CGC) has recently been developed in Japan, mainly to improve the durability of glass fiber reinforced concrete (GFRC). As part of the overall evaluation testing on the performance of GFRC using CGC and AR-glass fiber (New-GFRC), various properties of New-GFRC were tested, such as durability, compressive strength, flexural fatigue, flexural strength using a plank (thick specimen), resistance to freezing and thawing (ASTM C 666), dimensional change under storage in wet and dry conditions, and the adhesive strength between paint and GFRC. As a result of these experiments, it has become clear that New-GFRC excels conventional GFRC in all the properties of durability and both mechanical and physical properties.

In recent years, a high-tenacity acrylic fiber for technical applications was developed in West Germany. Test data using these special polyacrylonitrile fibers in mortar and concrete are presented. Within a limited parameter study, the amount and geometry of the fibers and the size of the largest aggregates of the matrix were varied. The produced specimens were tested concerning the flexural and compressive behavior as well as crack development due to shrinkage. To determine the optimal length of fibers, integral pullout tests were conducted. The modulus of rupture found in the experiments was used to show the effect of the fibers in a diagram that relates the size of the "plastic zone" to the critical crack width.

SP105 Leading edge design requires leading edge technology. "Fiber Reinforced Concrete Properties and Applications," provides the knowledge you need to design and build state-of-the-art concrete structures. Fiber reinforced concrete can be used in a wide variety of applications. With fibers being made of steel, glass, or polymer they can be added to the concrete mix in a variety of ways. Added to concrete in a ready-mix truck, cast in a conventional manner, or sprayed along with mortar slurry to form thin precast panels, new fibers, methods of manufacture, fabricating, and applications are being pioneered all of the time. "Fiber Reinforced Concrete Properties and Applications," a collection of 29 papers, is divided into five main sections: fracture and mechanical properties, polymer and glass fiber reinforced concrete, steel fiber reinforced concrete, pavements, and structural behavior. Topics such as: failure mechanisms and fracture of fiber reinforced concrete, fiber reinforced soil-cement, creep of concrete containing fibers and silica fume, development of lightweight durable fiberglass-reinforced concrete, flexural fatigue strength of steel fiber reinforced concrete, steel fiber reinforced heat resistant pavement, and flexural behavior and design of reinforced fiber concrete members are presented in great detail.