High performance fiber reinforced cement composites (HPFRC) are defined as the materials which exhibit a postpeak strain hardening type of response with a multiple crack pattern. Such a ductile behavior makes the HPFRC an ideal material to be used in structural repair and retrofit for dimensional stability, tensile-load carrying capacity, impact resistance, flexibility and long term impermeability. The critical parameter for continuous fiber reinforced cementitious materials to obtain the high performance response is the minimum fiber volume ratio with well dispersed fibers. As long as continuous fiber composites have a sufficient number of fibers to bridge the cracks, strain hardening and multiple cracking can always happen. However, there is no single dominant parameter which can control the multiple cracking process in discontinuous fiber composites. Various parameters can affect the postpeak response of discontinuous fiber reinforced cementitious materials. They are related to fibers, matrix and the processing methods. Parameters relating to the reinforcement include the type of fiber, fiber length, fiber volume ratio, fiber orientation, state of fiber dispersion and the degree of adhesion to the matrix. These primary variables are in turn influenced by selection of the matrix type, presence of additives, and the processing conditions. The latter acts through controlling the state of dispersion, establishing a fiber design a high performance fiber reinforced cementitious repair material, the approach in which the repair will be carried out should be considered simultaneously.

A large variety of materials and techniques are available to increase strength of existing concrete structures in an effort to extend their service life. The way to make repaired and strengthened concrete structures durable is to ensure that the new composite system is "tailored" to serve the intended service life, and that the composite human system, the team involved with a project, is knowledgeable and experienced enough to recognize the complexity of their task. The paper reviewed traditional methods and also offers a review on the use of advanced composite materials for strenghening existing comcrete structures. The advantages and limitations of different techniques are presented. It is concluded that, in the futrue, advanced composite materials will be widely used for repair and strengthening. To achieve this, it is vital that research and engineering education in cement-based and advanced composite materials are improved.

The performance of wollastonite-reinforced portland cement-based binders hydrated in saturated Ca(OH)2 solution, 1N NaOH solution, 1N KOH solution, distilled water and saturated moist air was evaluated as a precursor to the development of a test for assessing the durability of these composites. The cementitious binders are made of cement and silica fume. The effect of the different solutions on the mechanical behavior and microstructural characteristics of the systems investigated at 24 degrees Celsius and 80 degrees calicoes was determined. Porosity and pore structure determinations were made using mercury intrusion porosimetry, helium pycnometry, and isopropyl alcohol saturation techniques. Flexural strength and fracture toughness behavior was also determined. Pore structure modifications, leaching effects and mechanical test results were stability of wollastonite micro-fibers in cement binders. Wollastonite microfiber appears to merit serious consideration as a candidate reinforcement for the development of new composite systems.

SP-185 Up until now there has been very little information on the use of high-performance fiber-reinforced concrete (HPFRC). But recent laboratory studies and field applications show that HPFRC improves performance of civil engineering infrastructure in a cost-effective manner. This publication includes 11 papers on the mechanical properties of HPFRC for infrastructural repair and retrofit.

This paper reports the results of an investigation on the performance of FRC-encased open web steel joists under cyclic loading. The system completely eliminates the need for any shear connectors between steel joists and surrounding FRC as well as that for conventional longitudinal and transverse reinforcing bars, all of which are quite labor intensive. Cyclic load test on some half-scale specimens consisting of composite beams with end connections were carried out. The parameters included the configuration of web steel elements, and the amount of steel in longitudinal and web elements of the joists. The results are most encouraging. interact in a y so as to provide stable hysteretic behavior with excellent energy dissipation and ductuility. The study indicates that shear strength of the composite beam can be remarkably enhanced by addition of structures. The flexural capacity is also considerably increased. It can be quite accurately calculated by analytical models based on full composite action.