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Glass fiber reinforced concrete (GFRC) is a type of concrete that contains up to 2% alkali resistant silica fibers, replacing steel reinforcement and providing weight savings. It was first experimented with in Russia before World War II, but was unsuccessful due to erosion. However, in the late 1960s, an alkali-resistant fiberglass was created in Great Britain, leading to widespread use in Europe and Asia, and gaining popularity in the US. GFRC is commonly used for exterior cladding, garden pieces, and ornamental trim, and is also being used as an alternative to granite or quartz for countertops and other interior design elements. The main disadvantage is its cost, and it requires a specific curing process.
Glass fiber reinforced concrete (GFRC) is Portland cement containing up to 2% alkali resistant silica fibers mixed in. Fiberglass replaces steel reinforcement with great weight savings. The use of special alkali resistant glass fibers is crucial because concrete provides a highly alkaline environment which will destroy normal glass fibers.
Russian scientists experimented with using glass fibers in concrete before World War II without much success because the concrete caused the glass fibers to erode rapidly. In the late 1960s, the Building Research Institute of Great Britain created an alkali-resistant fiberglass. Since then, glass fiber reinforced concrete has been widely used in Europe and Asia and is gaining increasing market share in the United States.
In the United States, glass-reinforced concrete is used largely in the exterior cladding of tall buildings. Although usually only about 0.5 inches (1.25 cm) thick, these panels provide all the strength needed to withstand the elements. The most common finish used resembles stone.
Ornamental garden pieces and exterior trim are easier to pour with GFRC than conventional concrete. These include items such as statues, planters and fountains or corbels, teeth and railings. They can be thrown in empty, making them much lighter and therefore easier to move and install. GFRC is often cast to look like natural stone. It can also be treated with additives to make it water resistant, or treated and sheeted using a spray technique, which will generate a highly glossy, water impermeable surface.
These qualities made glass fiber reinforced concrete a commonly used work surface in Europe. Americans are starting to see these high-quality, attractive countertops as an alternative to granite or quartz installations. Some designers also use GFRC for fireplace surrounds, mantels and hearths. Further interior uses range from range hoods to furniture.
The main disadvantage of glass fiber reinforced concrete is its cost. It is much more expensive on a pound-for-pound basis than concrete. The current view is that for applications less than approximately 2 inches (5cm) thick, GFRC is the material of choice. It is considered too expensive to use for heavy pours, those 4 inches (10cm) or thicker.
Another disadvantage is that the concrete mix has a high concrete to sand ratio and a low water to cement ratio. This makes the spilled product prone to dry too quickly. Traditionally, GFRC panels have been cured in a humidity controlled room for seven days. A recent innovation adds acrylic solids or acrylic emulsions to the mix, which hold moisture and act as a curing agent and can cut curing times in half.
