From textured finishes to embedded photos, formliners open up a world of creativity.
By Claude Goguen, P.E., LEED AP
A big city wants its new football stadium to have a brick finish to give it a classic Midwestern fieldhouse look. A national park wants its shelters and bathrooms to have a natural wood appearance. A university wants photos engraved onto the walls of its new building. Despite the differences in aesthetics, these three real-life examples have one thing in common: the owners wanted to use precast concrete for its strength, resiliency and ease of installation while achieving a specific aesthetic. Fortunately, formliner technology allows them to have their cake and eat it too.
Most people think of flat, gray surfaces such as driveways or sidewalks when they think of concrete, but it can also be made into amazing pieces of art. Originally, laborious handcrafting was needed to create a desired pattern or texture. Materials like wood, stone, and steel were used to place a pattern into a concrete surface, but this provided limited options. In the 1960s, elastomeric urethane formliners were introduced in Europe, and soon afterwards, designers used them to bring their visions to the surface. In the 1970s and 80s, the ribbed pattern was very popular on retaining and sound walls, as well as many industrial buildings. Next, the polyurethane formliner came along, and the finish options expanded substantially. The simple repetitive patterns gave way to more natural and ornate patterns.
Today, just about any pattern or texture can be achieved. It’s not uncommon to see people walk up to a precast facade and touch it in order to believe it’s actually concrete.
As more roadways are constructed and existing highways are being widened, communities are taking advantage of precast concrete sound walls and retaining walls to put their local pride on display. Some walls may be adorned with ornate symbols while others may contain the name or crest of the local community.
There are a wide variety of formliners available to designers. The choice mainly comes down to number of uses, and type of finish and texture.
Formliners can be broken down into two types: single-use or multi-use. Single-use formliners are often made of styrene plastic and are less expensive and lightweight but may not offer the same degree of relief and texture depth. These can often be used as gaskets or holders for thin brick that are embedded into the precast wall panel. Liners hold the brick in place, providing consistency in the simulated brick mortar joints while the concrete is poured.
Styrofoam, which is often used for blockouts in precast concrete structures, can also be used to make single-use formliners. Polystyrene and acrylonitrile butadiene styrene (ABS) formliners will provide moderate relief and texture. These can be multi-use but are typically limited to 10 to 15 uses.
Elastomeric urethane (rubber) formliners are used to help attain more detailed relief and texture and can be used many times, more than 100 depending on the supplier. They are usually more expensive but can result in the best value when manufacturing products for larger projects that require more pattern and texture definition.
How they are made
Transforming concrete into a work of art involves many steps. However, it all starts with an idea. If the designer of a building wants the lower portion of the wall panel to have a pattern that resembles tall grass, conceptual drawings would be created and approved. Sometimes, the formliner manufacturer may also generate a 3D mockup for approval.
Once the pattern is confirmed, it is often converted by computer numerical control (CNC) software onto a master mold surface. The surface is carefully checked for accuracy and quality, and then sealed if necessary. At that point, the liquid resin or rubber is poured onto the master mold. Once the material has cured, it is removed from the master mold and carefully checked again before sending it to the precast manufacturer.
Once the precaster has it, they can place it in their form and pour the concrete onto it. The formliner will typically be at the bottom so the forces of gravity will help enhance the intricate details. Once the concrete has cured, the precaster will strip the piece, clean it and apply any other necessary treatments.
The finish options attainable using formliners is endless – from very miniscule textures to very deep reliefs. Imagine taking a photo and being able to transfer that image onto concrete through a formliner. That is what architects in Montreal, Canada, were able to do when they designed the Edison Residence.
An image captured by Thomas Edison of Montreal firefighters in 1901 was scanned into a computer which separated the color tones of the image. A machining file was created by the computer and fed to a CNC machine, which engraved the different grooves and textures on a master model. The formliner material was poured onto the master mold, and used to make the concrete panels. Once you stand back and look at the panel, Edison’s image comes alive.i
A similar process was used in Toulouse, France, for the Universite de Toulouse Paul Sabatier.
The concept of using a precast concrete facade to tell a story through images has spurred further innovations in formliner technology. US Formliner has a product called Artico Neo which is a plastic foil printed with an image or graphics and uses a concrete activator. This activator causes the concrete to set at different rates, like when using a surface applied retarder. This allows for a thin layer of paste to be partially removed as per the pattern of the activator. The contrast between the removed thin layers and smooth surfaces creates the image or graphic.
The primary value of precast concrete for owners, developers and designers has always been its strength, durability, energy efficiency and low maintenance. The advent and evolution of formliners are now adding another important value: the ability to express creative visions and ideas. Whether it’s to mimic a wood grain, add a medallion of the town’s crest or to tell a story through photos, formliners are tools manufacturers can use to enhance precast concrete’s versatility.
Claude Goguen, P.E., LEED AP, is NPCA’s Director of Outreach and Technical Education.