This Small Business Innovation Research (SBIR) Phase I project seeks to develop a new class of low-cost glass fiber composites that are compatible with the highly alkaline environment of concrete. The polymer matrix in these composites incorporates a fine dispersion of ion-exchange polymers for reducing the alkalinity of diffusing concrete pore water. Ion-exchange polymers are prepared by attaching polar groups to polymeric matrices; they are now produced at relatively low cost for use in filters and conditioners. The matrix incorporating ion-exchange polymers can feasibly act as a molecular sieve that removes alkali metal ions from the pore solution, and thus protects glass fibers against alkali attack. Preliminary analyses suggest that ion-exchange polymers possess the capacity, in the context of composite reinforcement in concrete, to lower the alkalinity of concrete pore water to levels that are not aggressive against glass fibers. Blending of conventional thermoset matrices of glass fiber composites with ion-exchange polymers promises to alter the favorable economics of glass fiber composites. This would facilitate large-scale introduction of composites as corrosion-proof and truly durable replacement for steel in concrete, noting that the relatively high cost of carbon and aramid fiber composites limit their potential for use as reinforcing bars in concrete.
The resulting composites should meet the demands on concrete reinforcement in terms of mechanical performance, bond strength to concrete and cost, and should also be chemically and dimensionally stable in the alkaline environment of concrete under diverse exposure conditions. Potential commercial applications of the technology cover reinforced concrete systems subjected to corrosive environments, including bridge structures, parking ramps and offshore structures.
