For every architectural project, once a mix design has been developed, sample panels should be built at the job site. These mockups serve as references for color and overall surface appearance.
White High-Performance Concrete (White HPC)
concrete (such as high-strength or very low permeability concrete)
adds high-tech appeal by incorporating materials like calcined clay
(such as metakaolin), slag, or white silica fume into white cement
concrete. Applications for HPC may include high-rise buildings,
bridges, and parking structures.
Supplementary cementing materials may slightly alter the color of hardened concrete. Color effects are related to the color and amount of the material used in concrete. Many supplementary cementing materials resemble the color of Portland cement and therefore have little effect on color of the hardened concrete. Some silica fumes may give concrete a slightly bluish or dark gray tint and tan fly ash may impart a tan color to concrete when used in large quantities. Ground slag and metakaolin can make concrete whiter. Ground slag can initially impart a bluish or greenish undertone.
The Romans referred to concrete as liquid stone. It was cement that allowed the most famous monuments and constructions of the ancient world to be completed, marking the most significant change in building design the world has ever seen. With the use of cement, architects were freed from the constraints of the past, from the limitations of quarried stone and its limited strength to size, from wood and the diminutive stature its buildings always possessed. Cement enabled the ancient architects to design with their imaginations, instead of their restrictions.
As anyone in the construction business surely knows, cement has not yet stopped evolving. The science of cement manufacture and production is continuing to make great strides, enabling new and imaginative processes to be invented.
Decorative concrete is on the forefront of this growth. With such techniques as dry pack cast stone, homeowners and designers can create an unlimited array of outdoor and textured surfaces and flooring options. These all enable the designers to escape the one flaw seen with concrete: as a finish material, its starkness can be downright plain. For instance, the durability of concrete makes it perfect for a driveway, patio, sidewalk or floor, so a means to "dress up" or disguise concrete without sacrificing any of the versatility is the goal of many of these manufacturers.
One of the first ways to transform concrete is through integral coloring. This is where pigment, usually iron oxides, is added directly to the mixer. The mix is then poured normally, producing a colored slab of concrete that will not fade because the color is literally a part of the mix. These colors can range from subtle pinks and browns to deep blues and greens.
This is usually done by adding a precisely measured bag of pigment to the concrete, taking into consideration the amount of cement, total yardage of the truck and individual properties of the chosen pigment. The drawback of this dry add-mix is apparent when trying to attain the same color for different amounts of cement. Because the pigment attaches to the cement, the same pigment added to a five-sack mix will be much darker than that of an eight-sack mix.
"By using four distinct liquid pigments, added together in the correct ratio (similar to a four-color printing process), a huge variety of color is available," then we measure and test the resulting pigment for accuracy.
Integral color has many uses for the concrete industry. Concrete roof tiles, garden accessories and pre-fab concrete pipe are all starting to use integral coloring.
Other methods of coloring concrete are more appropriate for different applications. For instance, many companies make both dry and liquid color hardeners that can be scattered or sprayed on top of newly poured concrete, and once worked into the surface, strengthen the concrete while allowing the use of any color.
One of the most popular methods for decorating concrete today is with the use of acid staining. Many residential and commercial customers are using this method for obtaining a durable, beautiful and relatively inexpensive way to decorate their floors.
While this concept is not new (Frank Lloyd Wright used some acid stains), innovative ideas are expanding the range of the acid stained look. Multiple stains may be used to enhance the depth of the color, grout lines may be cut into the concrete to resemble tile, or highly detailed murals or rosettes may be stained for any surface outside or inside the home.
Coupled with staining and stamping, a number of options are available for designing decorative concrete. Indeed, all of the processes described here can be mixed and experimented with, limiting designers to only what they can imagine. There are a few places for the curious designer to experiment with these options.
Master Builders (www.masterbuilders.com) may be widely known for manufacturing concrete materials, but they have recently helped produce an interactive online test grounds (www.concretelifestyles.com). The site allows the user to swap patterns and colors to see different styles.
The most impressive thing in outdoor and indoor concrete today may be what has yet to be constructed.
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