SBIR-STTR Award

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.

This Small Business Innovation Research (SBIR) Phase II project will refine the polymer matrix of glass fiber composites with ion exchangers in order to enhance their longevity in the alkaline environment of concrete. Glass fiber composites offer a desirable balance of performance and cost for replacement of corrosion-prone steel reinforcement in concrete; their rapid deterioration in the alkaline environment of concrete is, however, a major setback. Ion exchangers are insoluble solids carrying cations (or anions) which can be exchanged with ions of the same sign. Cation exchangers of hydrogen form replace alkali metal cations (e.g., K + in alkaline solutions diffusing into the polymer matrix) with H + . This exchange of cations neutralizes aggressive alkaline solutions by converting K + OH - (and Na + OH - , etc.) into H2O. Through laboratory investigations and industrial-scale pultrusion efforts, the Phase I research demonstrated that introduction of selected ion exchangers into the polymer matrix (or a surface layer of matrix) does not interfere with the pultrusion process, and yields significant gains in alkali resistance of glass fiber composites. The Phase I effort also established a theoretical context for selection of the dosage of cation exchanger in the polymer matrix of glass fiber composites, and verified the economic viability of our approach. The proposed Phase II project will: (1) develop refined theoretical principles and design procedures for formulation of polymer matrices with ion exchangers; (2) develop and experimentally verify optimum polymer matrix formulations incorporating ion exchangers; (3) optimize the pultrusion process of glass fiber composites with the refined polymer system, and fully characterize the end products; and (4) evaluate the structural performance and durability of concrete systems reinforced with refined glass fiber composite bars through comprehensive laboratory studies complemented with a field investigation involving design, construction and monitoring of a reinforced concrete bridge deck. The Phase II effort will receive critical support from major manufacturers of composite rebars (including Hughes Brothers, the world leader in this field), the leading supplier of ion exchangers (Dow Chemical), Michigan Department of Transportation, and Michigan Economic Development Corporation. Michigan State University (Composite Materials & Structures Center) will also take part in the proposed research effort. Close to one-third of reinforced concrete structures, including bridges, parking structures, buildings in coastal areas and offshore structures, are exposed to corrosive environments (deicer salt, seawater spray, etc.); domestic sales of steel for reinforcement of these concrete structures is about $2 billion/yr. Glass fiber composites embodying our technology are resistant to both corrosive effects and the alkaline environment of concrete; they offer a desirable balance of performance and cost to replace steel reinforcement in corrosive environments. Major savings in life-cycle cost can be realized at competitive initial cost through replacement of steel reinforcement with alkali-resistant glass fiber composites in concrete structures exposed to corrosive environments. Glass fiber composite jackets and sheets applied onto concrete surfaces for repair/rehabilitation purposes are also prone to attack by the alkaline pore solution of concrete, representing another market opportunity for our technology. We have filed a patent application, and have reached agreements with Dow Chemical (leading supplier of ion exchangers) and Hughes Brothers (world's leading manufacturer of composite bars for concrete reinforcement) towards transfer of the technology to marketplace