High strength carbon and glass fiber composites are being used to strengthen various types of reinforced and prestressed concrete structures. They are also being evaluated for strengthening of unreinforced masonry walls to improve their lateral and shear resistance. There is a critical need for this type of rehabilitation for structures located in earthquake prone areas and other locations that suffer natural disasters such as hurricanes. High strength organic matrix compounds have a number of advantages including high specific strength and resistance to corrosion. However, they are not fire-resistant. This deficiency becomes more important in buildings because fire not only reduces the effectiveness of the strengthening but could also result in toxic fumes. The results presented in this paper deal with the use of an inorganic matrix for strengthening concrete blocks. The matrix can withstand temperatures up to 1000 deg C and does not produce any fumes. Prismatic members cut from commercially available concrete blocks were strengthened with alkali resistant glass, E-glass, and carbon fibers and fabrics. The strengthened prisms were tested in flexure to evaluate the improvements in strength, stiffness, and toughness. The results indicate that all three types of fibers can be effectively used to improve the performance of concrete blocks. As expected, carbon fibers provide better reinforcement
