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Glass fiber reinforced concrete (GFRC) is beginning to gain popularity. It is a casting method that relies on spraying the cement mixture onto a mold rather than filling a mold, creating a hollow shell that can save on weight as well as time.
ENVIRONMENTALLY FRIENDLY CEMENT
The Portland cement typically used in concrete is not environmentally friendly. In the Portland cement manufacturing process, carbon dioxide is released into the atmosphere. Therefore, to make concrete truly green, one must reduce or eliminate the Portland cement. Portland cement is also troublesome in countertops in other ways, such as the propensity to stain and etch when exposed to foods and acids.
Concrete countertop makers use a variety of Portland cement replacements known as pozzolans, such as fly ash and slag, which are waste materials from coal burning and mining. The article “How to Make Environmentally Friendly Concrete” on the Concrete Connections Web site at www.ConcreteCountertops.net has more details about pozzolans as well as recycled/waste aggregate. These pozzolans, however, can only be used to replace a portion of the cement, because if too much is used, the strength of the concrete decreases.
There is a Portland cement substitute that can be used to replace up to 100 percent of Portland cement. This substitute is a type of fast setting cement. It is more environmentally friendly because the manufacturing process produces far fewer emissions. The elimination of Portland cement is a tremendous step towards making concrete countertops greener. Fast setting cement also has the major advantage of higher early strength and much faster turnaround.
GREEN SEALERS
It is important to consider sealers when discussing ways to make concrete countertops greener because many concrete sealers are not environmentally friendly. They contain harmful volatile organic compounds (VOCs) in the solvents used to dilute them.
Most sealer companies are moving toward water-based products instead of solvent-based. In fact, this change is mandated by state and federal agencies.
The difficulty with concrete countertop sealers is that there are so many factors to consider, such as cost, ease of application, stain/acid resistance, scratch resistance, heat resistance and maintenance requirements. Often an environmentally friendly sealer sacrifices one or more of the other factors.
