Concrete Furniture

Concrete furniture has been around for as long as concrete countertops have. In those early days, concrete furniture was primarily made out of precast concrete. Since it needed to be reinforced with steel, the concrete tended to be thick, massive and heavy. This made large, thin and delicate pieces impractical or impossible.

The current trend towards using glass-fiber reinforced concrete (GFRC) has changed that. GFRC is a form of concrete that has inherently high flexural strength. It can be easily shaped into complex, three-dimensional shapes that don’t need to be thick to be strong.

Furniture-making in and of itself can be challenging, since the object being made often has to be functional, ergonomic, durable, lightweight and portable. Plus, it has to be aesthetically pleasing. These challenges can be daunting when it comes to using concrete as the material of choice. Even GFRC, with its higher flexural strength and ease of molding, has limitations.

GFRC is concrete, but it’s the fiber reinforcement that creates the high flexural strength necessary for thin, lightweight shapes.

Flexural strength is also called bending strength, and it is this characteristic that is the most important when it comes to making a durable, high-strength material.

Conventional steel-reinforced concrete has two important and very different components: the concrete and the steel reinforcing material. The concrete is often an aggregate-based mix, but it also can be a mortar or all-sand mix.

Because the steel must be embedded inside the concrete and the concrete piece still has to be easily constructed, strong, steel-reinforced concrete beams tend to be relatively thick and therefore heavy.

In contrast, GFRC is essentially a single material that encompasses the concrete and its reinforcement. Yes, there is a thin, decorative, nonstructural face coat that hides the fibers, but the principal strength element is the GFRC backer coat, the bulk of the material. Because the glass fibers are mixed into the concrete, the strength is more or less the same everywhere. Not only is the material much easier to cast, but it behaves more uniformly, a great benefit to furniture that gets pushed and pulled and moved often.

That said, GFRC must be made correctly. The right kinds of fibers should be used in the right amounts and the concrete should be cast in the correct way.