Infrastructure in the United States such as bridges are degrading due to the corrosion of steel-reinforced concrete and steel structures by salty water and de-icing compounds. During the last years, structural retrofit work has come to the forefront of industry practice in response to the problems of an aging infrastructure and aging buildings worldwide. A type of repair frequently proposed to enhance the seismic resistance of bridge columns is the use of externally bonded sheets of fibers or the wrapping with filaments. For example, in Japan, retrofit applications for building and bridge columns were developed using carbon fibers and epoxy resin. In other countries, in particular in cold-climate countries, the corrosion effect of de-icing salts has a quite devastating consequence on the civil engineering structures. The repair and rehabilitation of these structures have become major challenges for the industry.
One recently proposed repair method consists of externally bonding flexible sheets of fiber composites with organic glues and resins. Another application for continuous fiber composites in infrastructure is the wrapping of concrete columns with continuous fibers with an organic matrix, to reinforce new construction and damaged bridges and buildings in earthquake and hurricane prone areas. The flammability of the organic polymer matrix of such fiber-reinforced composites limits the use of these materials in exposed interior building columns where flammability is a serious concern. Furthermore, even for outside uses, this susceptibility to fire currently limits the use of polymer composites in infrastructure, precluding any useful advantage in specific strength/stiffness and corrosion resistance compared to steel or concrete.
Thus, the major disadvantage of organic matrix fiber-composites is their lack of fire resistance and degradation under UV light leading to long-term durability problems. The carbon and glass fabrics can withstand normal fire exposure and are durable under UV light. But the weak link is the organic polymers used to attach these fabrics to concrete. It is also known that the most common failure pattern for concrete structures externally reinforced with organic matrix fibers or sheets, is their failure by delamination of fabrics at the interface of the concrete and fabrics. Delamination failure under utilizes the composite strength. Furthermore, this type of failure must be avoided in order to provide warning of the impending failure.
A variety of geopolymer resins are known, such as those disclosed in the Davidovits U.S. Pat. Nos. 4,349,386; 4,888,311; 5,342,595 and 5,352,427. Geopolymeric resins have been known for use as matrices in the manufacture of geopolymeric composites, e.g. fibers reinforcement composed of carbon fiber or graphite in a geopolymeric matrix (WO 88/02741, WO 91/13830, WO 91/13840, U.S. Pat. No. 4,888,311, U.S. Pat. No. 5,342,595, U.S. Pat. No. 5,352,427). Fiber reinforced composites with geopolymeric matrices of the aluminosilicate type described in the prior art do not ignite, burn, or release any smoke even after extended heat flux exposure. In general, geopolymer composites of the prior art are used to manufacture fire-resistant panels or structures for use in offshore oil platforms, military vehicles, aircraft and ground transportation, where fire endurance and firehazard are important. They are also used to manufacture items which work at temperatures ranging between 400.degree. C. and 1000.degree. C., for example devices for the casting of molten aluminum. However, the prior geopolymer resins of the above-mentioned documents have been found to not adhere well to iron, steel or concrete.