“Architectural concrete” refers to a building material that provides aesthetic finish, which may serve a structural function, too. In a broad sense, architectural concrete can be thought of as distinct from “decorative concrete,” which more typically refers to aesthetic flatwork or building elements, not structural building members. So in speaking about concrete for aesthetic purposes, both the terms “architectural” and “decorative” may be mentioned.

Concrete can take almost any form, texture, and color to satisfy the aesthetic and functional requirements of the structure—it offers surfaces that range from smooth to rough and a spectrum of color that ranges from the icy blue of quartz through the delicate pastels to the deep reds of decorative aggregates.

Architects and specifiers consider many factors when selecting color and texture for a concrete structure: the surface area, the viewing distance and angle, and aggregate particle shape and surface characteristics. When choosing a color, designers must consider that the surface appearance will change continuously throughout the day, and that the surroundings of the building will affect the color tone. Color selection should be made in lighting conditions that simulate the environment of the planned structure.

White portland cement is recommended wherever white or colored concrete is required. White portland cement is made of select materials that contain negligible amounts of iron and manganese oxides—the materials that give cement a gray color. Every cement, whether white or gray, has different inherent color tones as a result of slight differences in raw material ingredients and manufacturing processes. Architects should take this into consideration in the design process. When uniform color is critical, it is suggested to stockpile an adequate quantity of cement and aggregate so that consistent color results can be obtained.

Integrally colored concrete is made by adding mineral oxide pigments to concretes made with either white or gray cements. White cement is used when lighter shades of concrete are desired, but red, tan, and dark gray hues can be produced using gray cement.

An exposed aggregate surface is a decorative surface obtained by removing the outer layer of mortar and exposing the aggregate particles. This may be done with a variety of techniques, including chemical surface retarders, sandblasting, water blasting, or acid etching. Selection of aggregates is based on color, hardness, size, shape, gradation, durability, availability, method, and degree of exposure and cost. Popular decorative aggregates are natural materials such as quartz, granite, marble, limestone, and gravel, and manufactured materials such as alkali-resistant glass and ceramics.

Forms and form liners can be used to create textures and patterns that simulate, for example, brick, stone, and wood. Aluminum wall forming systems are available with brick-pattern faces, or with vertical rib or board-and-batten patterns. Also, a textured concrete surface will help camouflage the subtle differences in texture and color found on the surface of concrete.

In addition to concrete used architecturally (on buildings), other applications include:

• decorative flatwork


• hardscaping


• countertops

Decorative Flatwork

Decorative flatwork is usually considered to be an exterior use of colored and textured concrete. This makes it distinct from “floors,” which are interior concrete slabs. Flatwork includes cast in place pavements and curbs. More on decorative floors and flatwork.

Hardscaping

Hardscaping further identifies hard-surface materials as those which are used in exterior locations, like gardens, plazas, and for landscaping. Hardscaping is not limited to concrete materials; it includes masonry and wood surfaces, too.

The most popular hardscape surfaces made with concrete are patios, walks, pool and spa surrounds, benches, planters, retaining walls and similar applications. Cement-based products for hardscaping include pavers, cast in place concrete, and precast elements. More on hardscaping (PDF).

Countertops

Concrete countertops are yet another interesting application. First appearing in kitchens and baths in high-end homes and upscale and retail spaces, they have become increasingly popular in more modestly priced homes and commercial establishments. With a solid feel and unlimited aesthetic possibilities, they have found a niche alongside other upscale countertop materials like natural and manufactured stone. More on concrete countertops.

 
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