International Concrete Abstracts Portal

A brief review of the literature on cellulose fiber reinforced cement is presented, followed by the results of an experimental study concerned with the effects of mechanical and chemical pulps on the performance characteristics of neat cement paste in the fresh and hardened states. The mix proportions and manufacturing techniques used in this study for the production of cellulose-cement composites are reviewed. The air content, setting time, and drop in workability with time are compared for plain cementitious materials and those reinforced with 1 and 2 percent mass fractions of mechanical and chemical pulps. The flexural and compressive strength and toughness characteristics, impact resistance, specific gravity, and water absorption capacity of plain and fibrous materials are also compared. Effects of moisture content on the flexural performance of plain cementitious materials and those reinforced with mechanical pulp are discussed.

The fabrication, properties, and application of carbon fiber reinforced cement (CFRC) product made of coal tar pitch-based high-performance carbon fiber are presented. The experiments were conducted by mixing the chopped carbon fiber strands with cement and sand to obtain CFRC. The mixing test results revealed that this type of carbon fiber disperses quickly and uniformly in ordinary mortar. No special type of mixer is required. To optimize the characteristics of CFRC, experimental analysis was conducted on batches made in a mortar mixer regarding the fiber properties and mix proportion. The relationships of these parameters to the mechanical properties were examined. It was revealed that the parameters determining the apparent viscosity F (flow index) of CFRC slurries are fiber diameter í1, filament number n, specific surface area S, and fiber volume fraction Vf. It was also revealed that the parameters determining the strength of the hardened body were fiber tensile strength TS and Vf. The flexural strength of the 20 mm thick CFRC is about 3 to 4 times greater than that of plain mortar. This CFRC is also stronger and more durable than other FRC under the same conditions. High productivity, light weight, and weatherability characterize this new CFRC. These characteristics being appreciated, precast CFRC products have been increasingly used in construction in Japan. Some detailed descriptions of the practical applications are also made.

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-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

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