International Concrete Abstracts Portal

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.

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.

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.

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.

Traditionally, the first cracking strain of plain matrix is used as the material property in the fiber reinforced cement-based composites. It is used to indicate the tensile strength, and thus termination of the contribution of the matrix phase. In the presence of high volume fraction of fibers, formation of the first crack does not necessarily lead to the fracture instability; thus, matrix is able to carry increasing loads. The strength of the matrix is thus dependent on the type, volume fraction, bond, and strength of the fibers. Paper investigates the tensile stress-strain response of cement paste in the presence of glass fibers. A test procedure is described that can characterize the toughening effect of various fiber types on the matrix properties.