Development of Recycled Glass Paving Materials

Sandhill Industries, a woman-owned small business and manufacturer of glass wall and floor tile, has developed a process for manufacturing paving products made from 99 percent recycled soda-lime plate or container glass. The glass pavers are thinner, lighter, denser, stronger, and perform better in paving applications than brick or concrete. Furthermore, the manufacture of the glass pavers generates less than one-half of the greenhouse gases when compared with the manufacture of an equivalent amount of Portland cement concrete. Using the sintering properties of glass particles and a process based on ceramics and metals powders processes, Sandhill Industries has developed a process using no water and permanent stainless steel molds for improved energy efficiency. To date, the company has overcome technical barriers related to: (1) overcoming the tendency of soda-lime glass to devitrify when heated; (2) dramatically improving the appearance of fused mixed color glass; and (3) developing kiln profiles allowing the use of stainless steel molds, although stainless steel has a higher coefficient of thermal expansion than glass.The proposed project will: (1) test the glass pavers using American Society for Testing and Materials methods, (2) manufacture the pavers in a batch process as a Phase I commercialization pilot project, and (3) develop empirical data on the actual energy usage of manufacturing the pavers using a continuous kiln. The principal investigator has been involved with the development of recycled glass technologies for 10 years. Preliminary work performed on sintered glass products at the University of Washington indicated that the solid glass products had a 2:1 weight-to-strength performance advantage over concrete. By using a controlled devitrification kiln strategy, the glass pavers become nonabsorbent (freeze-thaw proof), as well as opaque and skid-resistant for outdoor applications.