International Concrete Abstracts Portal

Strength properties of steel fiber reinforced concrete and plain concrete specimens subjected to normal atmospheric exposure and accelerated cyclic testing in marine environment were examined. The concrete mix design consisted of cement:sand:aggregate in ratio of 1:1.96:3.01 with water-cement ratio of 0.6. The steel fibers, 10 mm in length, were added in volume of 0.0, 0.6, and 1.2 percent of the mix. Strength properties--compressive, flexural, and tensile strength of the concrete specimens containing steel fibers--showed considerable improvement over those obtained in the plain concrete exposed to the normal atmospheric condition. Both steel fiber reinforced and plain concrete specimens subjected to accelerated cyclic testing at 60 C, 24-hr cycle in marine environment, showed that the addition of fibers provided considerable improvement in strength properties. However, corrosion of the fibers was observed at or near the surface, and continued to worsen after 20 cycles. Specimens with 1.2 volume percent of steel fibers exhibited the largest increase in compressive and flexural strength in both test conditions, normal atmospheric and accelerated cyclic testing.

The background to the development of two types of thin, fabric-reinforced, portland cement concrete sheets is described and range of properties given. Both normal weight and lightweight mortars (including cellular mortars) were used as a matrix. Glass or synthetic fiber continuous reinforcement in the form of fabric scrims and/or nonwoven three-dimensional fabric were used. The materials developed are potential substitutes for plywood, cement asbestos, and other types of sheet material that require the properties of weather resistance, incombustibility, nonbiodegradability, and economy. The test results also suggest that the matrix and reinforcement concepts developed will lead to applications in other reinforced concrete uses. The thin sheet materials lend themselves to easy manufacture in a comparatively simple plant.

Thin-section fiber reinforced concrete is portland cement concrete or mortar reinforced with dispersed, randomly oriented discrete fibers. Fibers can be metal (low carbon or stainless), mineral (glass or asbestos), synthetic organic (carbon, cellulose, or polymeric), or natural organic (sisal). Fiber lengths can range from 1/8 inch to 2-1/2 inches. Furthermore, many existing thin fiber-cement composites on the market today comprise a blend of different fiber types. By ACI's definition, ferrocement is portland cement mortar reinforced by the number of very closely spaced layers of continuous fiber networks or meshes. Ferrocement can be manufactured with any of the fiber types mentioned above, even though its name might imply steel wire meshes. ACI Committee 544 and 549 organized international symposiums to address the many thin-section fiber-cement building products available the world or under development. SP-124 contains papers presented at symposiums in Atlanta, Feb. 1989 and in San Diego, Nov. 1989. Note: The individual papers are also available as .pdf downloads.. Please click on the following link to view the papers available, or call 248.848.3800 to order. SP124

The production of a polypropylene-reinforced cement material marketed as an alternative to asbestos-cement is outlined. Typical tensile stress-strain curves of a number of alternative materials are compared with asbestos-cement. The load-deflection characteristics of corrugated sheets made from nonasbestos materials are also presented and discussed. The nonasbestos materials are generally much less brittle than asbestos-cement, although they have a lower first-cracking strength. The pseudo-ductile behavior exhibited, with multiple cracking before the ultimate load is reached, means that permissible loads in service must not be based solely on ultimate loads but on cracking and possible deflection criteria. Less well-defined stresses arising during installation and from restrained moisture movements, which may crack the nonasbestos materials, are likely to be critical for the effective performance of new sheeting materials.

Flexural behavior of sandwich beams reinforced with thin layers of steel-fiber reinforced mortar was studied in this investigation. The effect of variations in thickness of the reinforced layer on the modulus of rupture, Young's modulus, and toughness of the member was investigated. This investigation considered one single specimen size with fiber reinforced mortar using one fiber geometry and content. Steel fibers with 0.6 x 0.3 mm cross section and 18 mm long were used. The specimens were cast in 100 x 100 x 350 mm molds. Eight series of sandwich beams with different thicknesses of the reinforced layer were tested. Experimental results indicated that sandwich beams can have strength and toughness comparable to fully fiber reinforced beams. The minimum thickness of the fiber reinforced layer required to impart ductile behavior to the sandwich beam was found to be about one-sixth of the beam depth.