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Architectural Concrete Panels
Decorative Home > Technical Documents > Architectural Concrete Panels

Aging Gracefully: Architectural Concrete Panels Turn 40 Years Old
by Jamie Farny, Program Manager, Masonry and Special Products

PCA architectural display in Skokie, Illinois

The PCA display consisted of a circular walkway in exposed aggregate concrete, inset with white cement concrete posts supporting two panels placed back-to-back.

The question of architectural concrete’s durability has been answered. A new report by PCA documents performance of 60 typical architectural finishes in a natural weathering exposure. Styles range from timeless classic finishes to 1960s-era design, but the techniques used to construct the panels are thoroughly contemporary.

Surface Aesthetics

The collection of panels was built to demonstrate various techniques for creating architectural concrete finishes, such as:

chemical retarders and sand-bedding techniques for horizontally precast exposed aggregate surfaces

form liners, rubber matting, plastic and wood forms for a variety of textures in horizontally precast panels

colored surfaces via powdered pigments integrally mixed into fresh concrete

two-layer construction, often with white portland cement and special aggregates contained only in the facing mix

tooled surfaces, including sandblasting, bushhammering, grinding and polishing, and surface-bonded sheeting

prepacked aggregate and gap-graded aggregate for vertically cast-in-place panels

After nearly 40 years of exposure to the Chicago area climate, panels were visually inspected and power washed. Ratings were made both before and after cleaning, and the findings are noteworthy. In addition to the panels, posts and walkways of the exhibit that were also cast in concrete were assessed during the display’s removal, and results reported.

The following images depict techniques and materials—some regular, some less common—used in the PCA display. Except for Panel 10, all panels shown here contain white cement for some or all of the matrix. Except for Panel 25, all panels were horizontally cast.

Panel 4: Polystyrene blockouts and chemical retarders allowed for surface textures, and lightweight concrete was used for the backup. Many formlined surfaces are still done in much the same way.	Panel 6: Plastic stencils and sandblasting created a swirl pattern. Stencils and sandblasting have recently been used for floors, too.	Panel 10: This panel is a forerunner of today’s wide array of formliners. Concrete contains lightweight shale aggregate and gray cement. Sharp edges were softened over the years by minor paste erosion.

Panel 15: Three aggregates in three colors—dark green, white, and pink—are combined for another exposed aggregate surface.	Panel 19: Pink feldspar aggregate makes a nice, somewhat sparkly pinkish-orange surface. This texture is very common for exposed aggregates.	Panel 25: Another example of exposed aggregate, this panel was vertically cast by first consolidating aggregate in forms coated with surface retarders, then removing the forms, washing and brushing away surface paste, and sandblasting to deepen the texture.

Panel 52: Broken pieces of marble tile were adhered to the form face and surrounded by mortar. Following aging for 60 days, the surface was ground and polished.	Panel 54: Special (non-reactive) glass in green gives a green-and-black effect because two sizes of aggregate were used. This panel also has excellent color retention.	Panel 55: Special (non-reactive) orange glass and brown aggregate give a surface with excellent color retention.

Durability and Long-Term Performance

Panels were rated either: excellent, good, fair, or poor. Most weathered extremely well, with 93% receiving an “excellent” or “good” rating. Most surfaces were sound and their appearance relatively unchanged. Slight etching or “softening” of the sharper edges was noticeable on a few surfaces, but not severe. Though some panels looked better after cleaning, many of them exhibited very minor staining from environmental sources (dirt, grime, pollution, etc.). Other than periodically cutting back vegetation to maintain a clear view, little maintenance occurred during the four decades.

Architectural Concrete Trends Today and in the Future

After presenting a detailed description of the panels’ construction, the report assesses the panels’ performance after long-term exposure, then covers current innovations that are changing the industry, and looks toward the future through design practices and environmental concerns that will shape the industry for many years.

For example, one current innovation in concrete technology, self consolidating concrete (SCC), is already having an impact on concrete construction, especially in precast construction. Several characteristics make SCC particularly interesting for use in precasting facilities. Most importantly, SCC produces a good surface finish. Construction time is shorter and production of SCC is environmentally friendly (no noise, no vibration).

Longer term, there is a developing environmental awareness in the design community, called “sustainability,” that has made the entire construction industry take a critical look at its practices. It is a holistic approach, helping designers and builders balance the economic, social, and environmental impacts of all actions taken to create the built environment. Concrete has an important role to play in sustainable construction.

As demonstrated by these panels’ performance, concrete is a responsible choice for sustainable development because it is durable. Concrete does not rust, rot, or burn, and requires less energy and resources over time to repair or replace. It is the most widely used building material on earth and has the longest lifespan of any traditional construction material.

Summary and Conclusions

This report can serve as an idea book and a time-saving teaching guide. The authors make an excellent case for the use of concrete for exterior walls: they are aesthetically pleasing, remain durable even after decades of exposure in an often harsh North American climate, and require very little maintenance—proof that architectural concrete is cost effective over the long term. Architects, contractors, ready-mix producers, precasters, and building owners, among others, will find this information useful when designing, building, or choosing building materials and construction techniques.

Much has changed since the panels described in this report were built, yet concrete remains a versatile choice architecturally and an excellent choice environmentally. Many of the methods used to create these decorative concrete surfaces became very popular, and remain nearly unchanged today, because they are effective. The basic processes of bringing out the best appearance of concrete walls remain similar to the original methods, while improvements in the past few decades have made techniques such as exposed aggregate, form liners, and pigmented concrete even more viable today.

For more information or to purchase a PDF of the full report, Performance of Architectural Concrete Panels in the PCA Outdoor Display(RD133), click here.