By: Grace Gallagher
November 24, 2020
Glass fiber reinforced concrete mimics the look and texture of concrete but is a fraction of the weight of traditional concrete. Glass fiber reinforced concrete, or GFRC, can be used in a variety of settings, from indoor renovations to exterior restoration projects, as it is an adaptable material that can be modified depending on its intended usage.
What sets GFRC apart from traditional concrete? GFRC is a cementitious material comprised of a mixture of fine sand, cement, acrylic polymers, glass fibers, and water. When these materials are mixed, formed, and cured, the resulting product is a durable, lightweight, concrete-like material that can be made to look and feel like concrete, precast stone, or traditional stone. The ratio of the materials used, as well as the specific types of polymers and glass fibers used in a mix, may differ depending on the application. The glass fibers provide tensile and compressive strength in the mixture, similarly to steel rebar reinforcement in concrete, however, the lightweight nature of glass fibers, GFRC is much lighter than traditional concrete. A variety of textures and colors can be achieved with GFRC depending on the admixtures that are included during fabrication.
GFRC has a wide variety of applications – it can be used to fabricate interior countertops, floors, fireplace mantles, exterior window surround elements, and façade wall panels, among other uses. GFRC is fabricated by either spraying the concrete mixture and glass fibers into forms, or by pouring a pre-mixed GFRC blend that includes the glass fibers in the mixture into forms. GFRC pieces that are fabricated using the “spray-up” process are typically stronger than pieces fabricated using pre-mixed GFRC blends because the glass fibers are longer and can be placed intentionally in the spray-up process, while the glass fibers in GFRC blends are shorter and randomly dispersed. Due to the higher cost of equipment and materials used in the spray up process, GFRC pieces fabricated using the spray up process are typically more expensive than those fabricated using pre-mixed GFRC blends. Designers should consider the intended use of the product – especially its aesthetic and weight-bearing expectations – when specifying whether the GFRC pieces should be fabricated using the spray up process or using pre-mixed GFRC blends.
Compared to traditional concrete and natural stone, GFRC has many obvious advantages: it is lightweight, which can help to cut shipping and installation costs; it is easy to achieve different colors, textures, and shapes; and it is more resistant to cracks and breakage due to the glass fibers dispersed in the material. GFRC can also be fabricated more quickly and cheaply than precast stone, natural stone, and concrete. However, it should be noted that GFRC cannot hold structural loads in the ways that precast stone, natural stone, and concrete may be able to. In addition, GFRC must be prefabricated using molds, and cannot be cast-in-place like concrete.
Whether you are performing an interior renovation project or restoring a building’s exterior, GFRC is a material that can greatly ease installation and cost worries during the course of a project. It is an adaptable material that remains a go-to product among architects, engineers, contractors, and building owners alike, and for good reason.