The use of glass adds a unique decorative element to concrete. How the glass is applied, the quantities of glass used and the mixes of colors chosen creates a customized design for a floor, countertop or other decorative concrete product limited only by the imagination.
Glass is used to create the ancient art known as terrazzo, which uses chips of glass, marble or similar material fixed in tinted cement, then ground and polished to a smooth sheen. Its beauty was discovered by mosaic craft workers in 15th century Italy, after noticing how small marble chips left on a terrace pushed into the surface, smoothed by foot traffic over time. The effect not only makes the floor unique, it strengthens the surface as well. Nowadays, architects and designers all over the world use the extremely durable terrazzo to create one-of-a-kind floors using vibrant, modern colors and transform environmentally sustainable surfaces into a stunning work of art.
Common Applications of Glass in Decorative Concrete
In this article, we’ll explore one of the most common applications of glass in creating terrazzo: integrally mixing. The process replaces all or a portion of the aggregate in a concrete mixture with recycled glass chips, creating a uniform look of glass aggregate and concrete in the finished product. Integrally mixing uses much more glass than other applications such as seeding, which will be discussed in our next article.
Steps for Integrally Mixing
- Replace traditional aggregate content with recycled glass chips on a 50/50 or any other percentage. If a 6-bag mix that requires 100 lbs of aggregate per batch, replace all or a portion of the 100 lbs with glass. More glass provides a more colorful finish, whereas less glass leaves a more subtle color.
- Mix, pour, bull-float, rough trowel and finish trowel the concrete.
- Cure concrete for about seven days, enough time to avoid damaging the surface by finishing too early, or damaging your tools by finishing too late.
- Begin grinding the concrete surface with a 50-grit diamond grinding pad. Increase to a 100 grit, then 200 grit and continue increasing the grit until you achieve the finish and polish you’re looking for. Avoid scratching or scarring the concrete by wetting the surface during the entire grinding process to reduce friction between the pad and the concrete.
- Sweep, vacuum or wash the surface (often with muriatic acid) to remove dust. Apply a sealer of your choice, carefully following the manufacturer’s recommendations.
*photo courtesy of American Specialty Glass
When you’re looking for quality glass for use in decorative concrete like terrazzo, count on Runyon Surface Prep. We carry American Specialty Glass products. ASG always recommends adding the fine glass product (ground glass minus 30 mesh) to your mixture when glass aggregates are used. The silica in the fine glass chemically reacts well with the cement to better bond the concrete mixture to the glass. The fine glass is lighter in color and is great for subtle color effects in concrete.