Development of Recycled Glass Paving MaterialsEPA Contract Number: 68D01043
Title: Development of Recycled Glass Paving Materials
Investigators: Kirby, Robert J.
Small Business: Sandhill Industries
EPA Contact: Manager, SBIR Program
Project Period: April 1, 2001 through September 1, 2001
Project Amount: $62,300
RFA: Small Business Innovation Research (SBIR) - Phase I (2001) RFA Text | Recipients Lists
Research Category: SBIR - Pollution Prevention , Pollution Prevention/Sustainable Development , Small Business Innovation Research (SBIR)
Description: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.
Economic modeling indicates that the glass pavers can be made for less then
$1 per square foot, and can be sold at prices that are competitive with brick
and stone paving. The new product will complement Sandhill Industries' current
marketing plan. The new product also will help Sandhill Industries as it expands
production into the lower
48 states. The feedstock for this manufacturing process, mixed color glass, is abundant in most larger municipal areas in the United States. For example, 15,000 tons per year of valueless mixed color glass are accumulated annually by Seattle's commingled recycling collection program. The economic model assumes that the glass can be purchased at the same price as "furnace-ready cullet" now being processed for the glass container industry.
Because the raw material currently is available in most larger cities, the manufacture of recycled glass paving products will have significant transportation advantages over the manufacture of Portland cement, stone, and brick, for which the raw materials often have to be shipped from mines to urban manufacturing plants and retail sales outlets. For glass, the raw material already exists "where the people are." Glass paving will never replace concrete paving for vehicular pavements. However, every new product for a traditional use involving recycled material and producing less greenhouse gases during manufacturing is both an improvement and an encouragement for others.