CWC Technology Brief
| Key Words |
| Materials: Glass.
Technologies: Press molding of remelted glass. Applications: Paving bricks. Market Goals: Access to local market. Abstract: Description of performance characteristics of glass paving bricks made from recycled glass. |
The Clean Washington Center sponsored a laboratory analysis of the output of a small-scale production system for manufacturing paving bricks from recycled glass. The analysis was perfomed by the Applied Technologies Laboratory of Western Washington University. Paving bricks were chosen for this project because they could be manufactured inexpensively using a single style with a large existing market and have the potential to absorb a large quantity of recycled material. The bricks are designed to be marketed as a highlight or detail in areas paved with standard clay brick.
The Product
The glass pavers manufactured for this project were the same length and width as standard paving bricks. The bricks were made from melted clear bottle glass with no additives or fluxes. The product has an amber-gray tint which many find appealing.
Production
The production system involved crushing glass and then passing the glass through a screen which retained any contaminants. The glass was then loaded into a furnace where it was allowed to melt and refine. Pouring was performed by ladling molten glass into a mold. After ladling the glass into the mold, while the glass was still malleable, the top of the mold was brought down and the glass was pressed into the desired shape. Annealing was performed in a closed temperature controlled vessel.
Laboratory Analysis
To qualify as a paving material, the physical characteristics of the glass bricks were required to meet or exceed standards for a generally accepted paving material. The bricks were tested against American National Standards Institute Specifications for Ceramic Tile. The results of the tests were as follows:
· Breaking strength: On average, the glass pavers tested at or over ten
times the 250 pound required breaking strength.
· Abrasive hardness: seven out of eight pavers tested above the standard of 50
grams for natural clay paving bricks.
· Coefficient of friction: Average coefficients of friction were .68 dry and
.47 wet. COF is normally agreed to between buyer and seller. The results compare
favorably with reference values for terrazzo and marble.
· Bond Strength: The glass bricks adhered to polyurethane sealant until the
sealant failed. More work needs to be done on cement mortar mixes to find an
adequate bonding material.
Potential Ventures
The possibility exists to develop small-scale manufacturing operations throughout the state. Facilities could be designed as turnkey operations and a manual of standard operation procedures could be created. A worksheet has been created estimating capital and annual operating costs for a small scale facility. Scaling the project up to a larger manufacturing facility is another possible option.
Other Applications
The recycled glass bricks may have other applications. Some interest has been shown in using the bricks as translucent panels in vertical applications. Some of the recycled glass bricks have been used with marble rubble in interesting floor samples. There also may be a potential market in sand blasting logs or images on the bricks and selling them as promotional, award, or decorative items.
Conclusion
The glass paving operation holds promise but more work needs to be done to make the recycled glass paver operation into a viable, repeatable model. In addition, a number of technical details of manufacture need to be worked out with glass production experts.
Report Dated: October 1994
Fact Sheet Update: October 1994