SBIR-STTR Award

Concrete, a primary building construction material, is the world’s most consumed man-made material. About 500 million tons of concrete were consumed in the United States in 2005. Production of cement (the binder in concrete) is an energy-intensive process and it contributes about 5 percent to global carbon dioxide (CO2) emissions. Production of each ton of cement results in the emission of 1 ton of CO2 to the atmosphere. Technova Corporation proposes to reduce the environmental and energy impact of concrete production, and to improve the performance and economics of concrete, through particle replacement of cement with milled waste glass. In 2007 about 13.6 million tons of waste glass were generated in the United States, and 76 percent of this glass was disposed of in landfills. The bulk of waste glass, which can be collected in mixed colors, has limited markets. Mixed-color waste glass, however, offers desirable chemical composition and reactivity for use as a supplementary cementitious material for enhancing the chemical stability, pore system characteristics, moisture resistance, and durability of concrete. To realize this potential, waste glass needs to be milled to micro-scale particle size for accelerating its beneficial chemical reactions in concrete. An exploratory study was conducted in the course of preparing the proposal for this SBIR project that confirmed the potential of milled mixed-color waste glass as replacement for approximately 20 percent of cement to enhance the structure and properties of concrete. Preliminary environmental, energy, and cost analyses point at the broad benefits that can be realized through large-scale implementation of the technology. There is a favorable match between the amount of waste glass that is disposed of in landfills and the amount of cement consumed in building construction for large-scale implementation of the technology. The environmental, energy, and cost benefits of the technology can be further improved because the technical benefits of milled (mixed-color) waste glass can enable effective use of demolished concrete as aggregate in new concrete building construction. The goal of this project is to identify the optimum particle size and dosage of milled mixed-color waste glass for use as partial replacement of cement in concrete, and to quantify the impact of the milled waste glass on the structure (chemical composition and pore system characteristics) and properties (mechanical performance, moisture resistance, dimensional stability, and durability) of concrete. The environmental, energy, and economic benefits of recycling mixed-color waste glass in concrete also will be analyzed further, and the competitive market position of milled waste glass as a supplementary cementitious material for use in concrete building construction will be assessed. Supplemental

Keywords:
small business, SBIR, EPA, green building materials, construction material, cementitious material, mixed-color waste glass, waste glass, recycling, concrete, CO2, carbon dioxide emissions, environment, energy-efficient construction

Production of cement (the binder in concrete) is a highly polluting and energy-intensive process, accounting for about 6% of global, anthropogenic C02 emissions and close to 2% of worldwide primary energy use. This project focuses on partial (~20%) replacement of cement in concrete with milled (mixed-color) waste glass to improve the moisture barrier qualities, durability, dimensional stability and other engineering properties of concrete. These beneficial effects would be realized as far as waste glass is milled to micro-scale particle size for accelerating its chemical reactions with cement hydrates. The landfill-bound quantities of glass are adequate to significantly impact the concrete construction practice. Waste glass is generated largely in urban areas, where the bulk of concrete production also takes place. Broad use of milled waste glass in concrete would yield significant environmental, energy, and cost benefits, and also would enable more extensive use of recycled aggregate concrete. The Phase I effort identified desired particle size and dosage of milled (mixed-color) waste glass for beneficial use as partial replacement for cement in concrete. The favorable effects of milled waste glass on the chemical composition, microstructure, and key engineering properties (including stability under potential alkali-silica reactions) of normal and recycled aggregate concrete were identified through laboratory investigations. Theoretical and numerical studies were conducted to rationalize the experimental observations and to assess practical implications of using recycled glass concrete. A successful field study also was implemented in collaboration with concrete and recycling industries. The environmental, energy and (initial and life-cycle cost) benefits associated with partial replacement of cement with milled waste glass were quantified using the outcomes of Phase I effort. The proposed Phase II project will: (i) expand the experimental database on recycled glass concrete to cover broader ranges of concrete materials and engineering properties; (ii) corroborate the statistical significance of the benefits rendered by milled waste glass and verify the statistical control over production of recycled glass concrete; (iii) identify the mechanisms through which milled waste glass benefits the engineering properties of normal and recycled aggregate concrete; (iv) thoroughly assess the gains in service life and life-cycle economy of major concrete-based infrastructure associated with the use of milled waste glass; (v) implement and monitor large-scale field projects to demonstrate the scalability, compatibility with prevalent construction practices, and practical value of recycled glass concrete; and (vi) evaluate the environmental, energy, and cost benefits of recycled glass concrete in different applications and service environments.