About 110 years ago, a new city demonstrated how sustainable communities should be built using precast concrete. John Alexander Brodie, an English engineering legend, unveiled his concept of prefabricated concrete housing technology at the Cheap Cottages Exhibition at Letchworth, England. Hardly a household word today, at the time, this quaint community drew international attention. It was one of the world’s first “new” towns.
Brodie’s precast structures in the “new” towns received a lukewarm reception. Only one of these structures exists today, but in 2017 the engineer’s vision may finally become fulfilled. Precast concrete may have come of age due to renewed interest in offsite prefabrication of building elements.
In a 2016 National Institute of Building Sciences survey, 33% of responding general contractors anticipated using more offsite construction in the next year; 50% expected to use the same and 9% anticipated using less. For many innovative contractors, offsite construction has the advantages of a safer and more controlled environment for workers. By allowing key components to be fabricated inside a closed factory, there is less need for highly skilled labor are less high-risk work.
Construction experts suggest that general contractors should review every construction project to determine which, if any, components of the project could be built offsite. While opportunities for a full offsite project are rare, it’s still important to search for a hybrid approach that implements both traditional onsite and offsite methods.
Precast concrete offers a perfect tool in this hybrid approach. There are several reasons precast concrete is poised to become the preferred off-site building material. These include durability, factory-quality performance, decorative elements, and contributions to resiliency and sustainability.
More than a pretty picture
A dozen or so years after Britain’s Cheap Cottages display, concrete engineers began developing the concept of architectural precast concrete. John J. Earley, an American civil engineer, was the leading advocate in texturizing precast concrete surfaces for the first half of the 20th century. Earley described his mosaic method as “a comparatively thin surface layer of expensive, special aggregate concrete and an ordinary backing mix which was revealed by water-washing at the correct curing stage.”
For the balance of the 20th century, especially in post-World War II construction, precast exposed aggregate concrete cladding was a widely accepted architectural style. Most designers adopted styles based on the Earley method. But as architectural precast concrete moves into its second century of development, producers and architects are expanding the material’s appearance with new products and production techniques.
In the 1990s, Finnish architect Samuli Naamanka began his work on architectural precast after completing a course on concrete applications at the Helsinki University of Art and Design. His interest became inspiration. He worked to create a product that could be used to cast textures and designs on large-scale concrete surfaces, allowing architects to design more visually creative structures.
Naamanka’s efforts culminated with Graphic Concrete, a patented method of creating patterned concrete surfaces. In 2000, he launched an effort with leading Finnish concrete producers, paper manufacturers, and printing laboratories to adapt the technology for precast concrete production. This was a success and in 2003 Graphic Concrete Ltd was founded.
Today, Graphic Concrete is a proven concept in the precast concrete industry. During the last 15 years, concrete producers and architects have employed the Graphic Concrete process on more than 600 projects in 25 nations. The manufacturer boasts of many high-profile public, residential, commercial, industrial, and infrastructure projects.
Graphic Concrete provides a practical solution for creating impressive architecture with a high-quality, yet affordable, concrete panel. The vehicle is a membrane imprinted with the design using a surface retarder. Graphic Concrete sends the membrane to the precast producer, who casts concrete onto the membrane. When the retarder is washed away the image is revealed. The image results from the contrast between the smooth wall panel surface and the exposed aggregate.
Producers have found it easy to incorporate Graphic Concrete into their standard production procedures for wet-casting surfaces. Many customers opt to select from GCCollection, a collection of ready-made patterns. Or, upon request, the Finish team can work directly with the project’s architects and designers to tailor the design so that each project’s outcome is unique. Producers can also incorporate other decorative production techniques, such as different aggregate or colors, to increase the variations.
Graphic Concrete also confers with the producer about the concrete mix design and production procedures. Each producer must comply with Graphic Concrete’s operating standards. Since producers are asked to limit vibration during placement, most elect to use self-consolidating concrete.
Facade Systems Inc. Toronto, Ont., represents Graphic Concrete in North America. Blair Davies, Façade System’s founder, has almost a decade of service in the industry. “We are looking forward to working with more precasters as we expand our presence in North America,” said Davies.