The effect of material constituents on the performance of fiber reinforced cementitious thin sheets was studied in order to examine the possible trade-off between cost and performance in cement-based building product development. A variety of materials were incorporated into fabricating cementitious thin sheets. The variables included types of fibers (glass, polyethylene terephthalate, polyolefin, or polyvinyl alcohol), types of sand (marble, silica or fly ash) and percent content, mixing method (dispersive or non-dispersive), latex types (MMA or SB), cement types (Type I or Type III), mineral additives (metakaolin or silica fume) and curing conditions (moisture or steam). Twelve batches of thin sheets with 3% fibers by volume for each were prepared by extrusion processing and three-point bending tests were conducted to evaluate the strength and toughness. The purpose of the study was to establish several mix designs for extrusion production of high performance fiber reinforced cementitious thin sheets at compatible cost.

It is well known that glass fiber cement composites may suffer a loss of strength and toughness when exposed to natural environments. Even though buildings in Europe clad with GFRC panels have performed well for nearly 30 years now, this has restricted its use in certain circumstances because of a lack of confidence on behalf of the designer and specifiers. The loss of long term properties of GFRC is explained by two main phenomena: 0 The chemical attack of the glass fibers. 0 The morphological modification of the interfaces due to the growth of hydrates (Ca(OH)2 + CSH) which leads to em brittlement of the fibers in the matrix. The most widely used solution against the first type of attack is to use Alkali Resistance, AR, glass fibers with Cem-FIL being the original and Cem-FIL 2 giving the best long-term results. However, the way to obtain both constant flexural strength and ultimate strain (toughness) is to use both AR fibers and to modify the cementitious matrix in order to optimize the nature of the hydrate in the interface between the fiber and the matrix. Until recently, no totally satis-factory solution has been found even with the use of low alkali cements such as calcium sulpho-aluminate cement or portland cement with silica fume or flv ash. The CEM-FIL Star mix, developed by the Saint-Gobain group some 1 0 years ago, now has worldwide experience. It is based on using AR fiber with a specific type of the manmade, and therefore controllable, pozzolanic mate-rial, metakaolin, with a portland cement matrix. This reacts in a controllable way with the liberated lime, (calcium hydroxide), thus eliminating the main reason for the embrittlement of GFRC with time. By reacting with and re-moving this lime, long-term properties are improved.

A class of new structural materials with a significant degree of ductility and strength are introduced that are durable, strong, and cost effective. High fiber content cementitious materials (FRC materials) are manufactured using a computer controlled closed loop system for pultrusion and filament winding. Composites consisting of unidirectional lamina, and [0/90/0] are manufactured. In addition, sandwich composites with a lightweight aggregate core and 0/90 lamina as the skin elements are studied. Mechanical response of laminates is measured using closed loop uniaxial tensile and flexural tests. Results indicate that tensile strength of composites containing 5% alkali-resistant (AR) glass fibers can exceed 40 MPa. The ultimate strain capacity can also be increased to more than 2% using cross plies at various orientations. Significant cost savings and weight reduction may be achieved by replacing the inner layers of the boards with a lightweight aggregate mixture at a marginal loss of strength. The ultimate strain capacity of the composites is a function of ply orientation, thickness, and stacking sequence. Various mechanisms of delamination, debonding, and crack deflection are identified, resulting in an ultimate strain capacity of 2%, and a fracture toughness as much as two orders of magnitude higher than the conventional FRC materials. The extent of matrix cracking, ply delamination, and crack deflection mechanisms are studied by means of fluorescent microscopy.

The steel free bridge deck slab technology has seen its real-life applications in a span of less than ten years from its initial conception. Indications are that more and more bridges will be built using this concept around the world, especially in places where corrosion of reinforcement is a serious concern. In this paper, results of an experimental project carried out at the University of British Columbia, where a full scale bridge deck was tested with carbon fiber reinforced cement (CFRC) permanent formwork, are described. The bridge deck had 0.4% of fibrillated polypropylene fiber reinforcement but no traditional steel reinforcement. The carbon fiber used in the formwork was a pitch-based fiber with a moderately high modulus of elasticity and tensile strength. The deck slab was tested at various locations under a simulated concentrated wheel load and the load vs. deflection characteristics were recorded. While the bridge deck failed, as expected, in a punching shear mode at a load several times higher than the design load, the bond between the CFRC formwork and the concrete deck was identified as a weak link in the system

Composite cement boards emerged as some of the more innovative and highly promising engineered building materials. Such materials found their use in construction applications such as tile backerboard or EIFS substrate, where exposure to elements, water or high moisture, prevents the use of conventional gypsum- or wood-based products. These cementitious boards, typically 12.7 mm thick, usually consist of an aggregated Portland cement-based core matrix, reinforced with glass fiber materials. Virtually all boards developed and manufactured in North America employ two layers of glass-fiber scrim embedded on both sides of the board, just under the surface. To prevent alkali attack on the glass in the high pH environment of the cementitious matrix, the scrim is coated during manufacture using specially formulated PVC plastisols. This paper discusses the long term performance aspects and the comparative assessment of various woven and non-woven plastisol-coated glass fiber fabrics in thin cementitious products. The importance of proper plastisol coating, its formulation and application, is shown as well. Potential next generation of alternative reinforcements of fabric-faced cementitious boards, such as resistant AR-glass-based scrims and highly promising, patent pending developments of composite glass / polymer fibrous mesh reinforcement grids is reviewed as well.