International Concrete Abstracts Portal

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

A cementitious matrix capable of dispersing fibers using conventional mixing techniques was developed. The effects of reinforcing this matrix with different volume fractions (0 to 2 percent) of aramid fibers ranging in length from 1/8 to 1/2 in. (3 to 12.7 mm) on the composite material performance in the fresh and hardened states were assessed experimentally. The effects of matrix mix proportions on the fibrous material properties were also investigated. The test data generated in this study indicated that improvements in strength and toughness characteristics of cementitious materials can be achieved through aramid fiber reinforcement, with no need to use specialized manufacturing techniques.

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.

Thin-walled, nonload-bearing exterior building facade panels of glass fiber reinforced concrete (GFRC) are manufactured by the spray-up process. Controlled factory conditions with strict attention to quality control are essential to help assure manufacture of a high-quality product. Furthermore, careful attention to installation and erection procedures cannot be overlooked. Paper describes the authors' experiences during their involvement in several major GFRC facade installations. Observations made during successful GFRC panel applications, and lessons learned in evaluation of GFRC facade failures, have formed the basis for development of an effective Quality Control/Quality Assurance (QC/QA) program that has been successfully implemented. Paper addresses QC/QA aspects of panel manufacture and installation that go beyond guidelines given in the PCI Recommended Practice. Methodologies presented in this paper will be a valuable tool for owners, designers, manufacturers, and contractors participating in the manufacture and installation of GFRC facades.