Concrete – The Architect’s Clay

By Earl Hunsinger

When you think of concrete and steel, you may think of a factory or an office building. Do you think of home? Of course, for many city dwellers, apartment buildings made of concrete and steel are the only homes they’ve ever known. However in recent years, concrete and steel have also increasingly become the building material of choice for single family dwellings.

It has been estimated that internationally over five billion cubic yards of concrete are used every year. This makes it the second most consumed substance on earth, after water. This isn’t surprising when you consider that it has the compressive strength of stone, yet can be poured into any shape desired. When steel is added to increase the tensile strength of the finished product, it becomes an incredibly strong and versatile building material. Such reinforced concrete has been used for over a century, especially in cities, to provide safe and durable multistory buildings for a variety of uses.

If the thought of a concrete home calls to mind a gray, boxy, utilitarian office building, or worse still a factory, you may be reluctant to even think seriously about concrete as a building material. It’s true that concrete is often gray and is usually given a smooth finish. It is most often used for flat walls, floors, etc. Yet, it doesn’t have to be gray; it can just as easily be given color, even vibrant color. At the same time, it can be given a variety of textures and patterns.

Would you like curved walls, arched doorways, or domed ceilings? While these often pose a challenge when using more traditional building materials, with concrete, they are readily achievable. Concrete is to an architect what clay is to a sculpture. This means that practically the only limit is your imagination.

One way of utilizing concrete is a technique called insulated concrete forms or ICFs. These forms are made of expanded polystyrene and stacked like building blocks to form the exterior walls of a home. They are then reinforced with steel and filled with concrete to form solid, seamless, fully insulated concrete walls. This system provides for an effective R-40 energy rating or better, compared to an R-20 or so value for a typical new wooden frame construction.

Because of the versatile methods available for forming and shaping concrete, it can be used for practically any style of construction. For example, it is often used in place of adobe to create low maintenance southwestern style homes. Whether concrete is used with ICFs, or in a more artistic, free form technique, concrete homes are durable, quiet, and provide a measure of safety from fire and storm. In addition, the larger thermal mass of the concrete eliminates the high and low temperature extremes that some wooden homes experience.

Recently, some fundamental assumptions about the nature of concrete itself have been challenged. This may lead architects to new forms of expression using concrete. For example, self consolidating or self compacting concrete is a highly flowable (thin) concrete that (among other uses) can be poured into molds to create an exceptionally fine surface texture. The Lafarge Corporation has developed another concrete innovation. Their product, Ductal®, incorporates extremely strong fibers in the concrete to make it self reinforcing. This means that thin concrete objects, such as structural members, can now be created that are as strong as metal. If those innovations don’t excite you, how about concrete that you can see through? By mixing glass fibers into the concrete, researchers are currently experimenting with ways to create concrete that is translucent.

All this means that perhaps someday in the not too distant future, when you think of concrete, you won’t be thinking about work. When you think of concrete, you’ll get that warm, relaxed, peaceful feeling that is only inspired by thoughts of home.