International Concrete Abstracts Portal

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.

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

Thin-walled glass fiber reinforced concrete (GFRC) panels are used as facade systems for commercial structures. Wind load and gravity load are primary load cases typically considered in panel design. However, since the GFRC skin is relatively thin, it responds rapidly to thermal and moisture variations. Therefore, minimizing restraint of the GFRC skin movement under varying environmental conditions and/or determination of stresses resulting from restrained movement are also primary considerations in GFRC facade panel design. Paper addresses concepts for design of GFRC panels including material behavior, design strengths, and loading combinations. Discussions of load conditions and recommended design considerations are presented for the effects of manufacturing, handling, and erection loading, gravity loading, wind loading, and loading due to external and internal restraint of moisture and thermal movements. Paper is based on the authors' experiences during their involvement in the design process for several new GFRC installations along with observations made and lessons learned in evaluation of GFRC facade failures

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.

Precast thin ferrocement planks have replaced wood for a variety of applications. Present knowledge about joining them using steel bolts or similar means is very limited. While bolted connections are commonly employed in steel construction, their suitability for connecting precast reinforced concrete or ferrocement elements is yet to be fully investigated, particularly when subjected to both bending and direct tension. A series of tests were carried out at the Structural Engineering Research Centre, Madras, India, on precast ferrocement planks connected together using steel bolts for transferring tension and flexural moment