International Concrete Abstracts Portal

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

Describes the investigation of a new range of cellulose fibers suited to the reinforcement of a portland cement matrix. This investigation indicated that fibers selectively derived from high-density summerwood are better suited for reinforcement than is the unmodified pulp that contains a large measure of fibers derived from springwood as well as summerwood. Another cellulose fiber material, termed expanded fiber because of its finely fibrillated microstructure, was indicated to have potential as a processing aid. Expanded fiber displayed excellent suspending and retention properties and imparted relatively high uncracked strength to finished composites. Overall, substantial performance differences were observed comparing, tests on wet versus dry specimens and the long-term durability was not evaluated. Despite these limitations, flexural stress/strain performance of the cellulose reinforced composites compared quite well to asbestos and glass fiber reinforced composites. The cellulose composites had substantially more ductility than asbestos cement; in this regard, the load-deflection curve was similar to glass reinforced cement.

Treatments of AR glass fibers in silica fume slurry prior to their incorporation in cementitious matrix was found to be an effective means for improving the durability performance of GFRC composites. The improvement was found to be dependent on the extent of penetration of the silica fume particles into the spaces between the filaments during the slurry treatment. In a glass fiber fabric, heavily coated with polymer, the penetration was hindered and therefore the advantage offered by the silica fume treatment was not as great as in continuous glass fiber strands that were more readily wetted by the slurry.

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.