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Home > Publications > International Concrete Abstracts Portal
The International Concrete Abstracts Portal is an ACI led collaboration with leading technical organizations from within the international concrete industry and offers the most comprehensive collection of published concrete abstracts.
Showing 1-5 of 22 Abstracts search results
September 1, 1990
A. Bentur, S. Mindless, and c. Yan
Thin-section fiber reinforced concrete (FRC) panels may be subjected to localized impact. In this study, thin sheet FRC materials, made with asbestos fibers in different matrixes, were tested under impact loading, using a drop-weight instrumented impact machine. The impact properties were characterized in terms of the peak bending load and the fracture energy (computed as the area under the load-deflection curve). Companion specimens were tested under static loading. The specimen dimensions were about 200 mm wide, 600 mm long, and 6 to 12.7 mm thick. In all cases, the peak bending loads were considerably higher under impact loading than under static loading; however, the fracture energies were always higher under static loading. These effects can be explained in terms of the porosity of the interfacial matrix, and the degree of bundle separation of the asbestos fibers.
M. A. Sanjuan
Fibers are added to concrete to improve several of its properties. The ability of polypropylene fibers to modify different characteristics of concrete is controversial. This paper presents results on the influence of adding polypropylene fibers (0.1 to 0.2 percent by volume) on mortar permeability and plastic shrinkage. The influence of adding polypropylene fibers on the early stages of shrinkage is studied with 120 x 15 x 3 cm specimens. These were fabricated in mortar and then held in a chamber with controlled temperature and ventilation. The specimens have a special geometry to enable the shrinkage measurement in the plastic state, and the influence of this on mortar cracking. The variables studied were: water-cement ratio, sand-cement ratio, and fiber content. In addition, the ability of fiber concrete to absorb water and its permeability to CO2 were tested. Water absorption was measured in accordance with French standard NFB 10.502. Carbonation was studied by introducing fiber mortar specimens in a chamber saturated with CO2 and comparing the results with natural carbonation. Results show that the addition of fiber reduces plastic shrinkage when compared with the same type of mortar without fibers. Concerning water absorption, it is reduced when water-cement ratio is about 0.5; however, when the water-cement ratio is higher than 0.5, this behavior is reversed and the fiber mortar is more water absorbent. Accelerated and natural carbonation show that CO2 diffusion increases in mortar with the highest amount of fibers.
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.
Kenneth D. Vinson and James L. Daniel
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.
I. R. K. Greig
The inherent light weight, toughness, low permeability, smooth surface finish and resistance to shrinkage cracking have all contributed to GFRC being an attractive alternative to traditional materials in the following areas of mining: 1) stabilization of rock tunnels by in situ spraying of thin skins; 2) construction of ventilation stopping walls both by a surface bonding technique and as a direct substitute for simple lime and sand mortars; 3) fire protection of timber packs by lightweight GFRC renders with improved adhesion and impact strength; 4) manufacture of drainage channels which are lighter in weight than their concrete counterparts and tougher than the asbestos cement alternatives; and 5) production of permanent formwork, which is lighter in weight and has a better surface finish than concrete and is much more efficient than the use of temporary shuttering.
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