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Concrete stucco is a surface finish that consists of cement, sand, and water. It is essentially a plaster that can be applied to both interior and exterior wall surfaces. The color and texture of concrete stucco is dependent on the rocks, pigments, and mixing technique used to create the plaster.
The color of concrete stucco is determined in part by the color of the aggregates — the elements that make up mixture. The aggregates of concrete are sand and gravel. The color of these elements will go a long way in determining the color of the concrete stucco.
Another factor which contributes to the color of concrete stucco is mineral oxide pigments. These are added to the plaster mix to alter the color of the stucco. There are several pre-pigmented cement mixes which can also be used to modify the color of the concrete stucco. Several types of manufactured finish-coat concrete stucco are also available in different tones.
The texture of concrete stucco is determined by the size of the aggregates. Sand has a smaller particle size than gravel. Gravel is 0.079 to 2.5 inches (2 to 64 mm) in size, while sand is 0.0025 to 0.0787 inches (0.0625 to 2 mm). Plaster mixes that contain more sand generally produce a stucco finish that is smoother than mixes which contain gravel.
Another contributing factor toward the texture of the stucco is the consistency of the finish mix. This can be controlled by adjusting the speed and duration of the mixing process. Plaster that is mixed for a short duration and at a slow speed will have a thicker consistency than plaster that is mixed at high speeds and for a longer amount of time.
The texture of stucco is very important because it gives structure to the surface. It provides highlights and depth to the building, as well as visual continuity. Certain textures can also create the appearance of other types of construction materials, including wood timbers and brick.
Typically, 0.5 inches (1.27 cm) of plaster is applied directly onto the surface of a concrete wall. To reach that thickness, two to three coats is often required. Generally, the plaster is resistant to impact and it repels water.
When the plaster is applied to a metal surface, usually three coats are required, producing a thickness of about 0.875 inches (2.22 cm). For metal surfaces, a building paper is usually placed over the surface before the plaster is applied. This paper is water-resistant but vapor permeable, allowing air to pass through.