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 simplified analytical procedure is proposed to predict stress-strain diagram of ferrocement composites under tension. A fracture mechanics approach is used to predict the load at first cracking. Results of a limited experimental investigation are also shown and used to evaluate the analytical model. The influence of curing is also demonstrated experimentally.

Presents comprehensive test data on the flexural strength, deflection, and cracking behavior of thin sheets of 6 to 13 mm thickness reinforced with a wide range of reinforcing elements. Two different sizes of sheets were generally tested under four-point loading, and in the case of glass fibers, a further small laboratory scale test specimen was also tested. Five different types of reinforcing elements were used: steel fibers, welded steel mesh without and with steel fibers, two types of woven polypropylene fabrics and glass fibers. The matrix was designed for durability and high workability with low water-binder ratio and a superplasticizer. In addition, 50 to 70 percent of the portland cement was replaced by fly ash. Extensive test data are presented and compared in terms of limit proportionality, modulus of rupture and cracking. It is shown that a wide range of reinforcement elements can be successfully used for thin sheet applications, and that the performance characteristics of thin sheets are very much a function of the type, geometry, and volume fraction of the reinforcement.

Presents comprehensive test data on the tensile behavior of 12.5 cm thick ferrocement plates. The main variables investigated were mesh geometry, specific surface, volume fraction, mesh yield strength and skeletal bars. The specimens were specially designed to insure failure in the gage length. The matrix was proportioned for high strength, high workability, and high durability with low water-to-binder ratio, and 50 percent fly ash replacement. Cracking and deformation were monitored throughout the loading range. The results showed that the composite properties of elastic modulus and ultimate tensile strength could be satisfactorily predicted. However, the cracking behavior for a wide range of mesh geometry could not be satisfactorily predicted by a single unique relationship. There was, however, good correlation between the composite properties of ultimate tensile strength and ultimate flexural strength. The results show that by suitable design of the matrix and the reinforcement, high-strength, ferrocement sheets with high crack resistance can be developed for a variety of structural applications.

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.