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Matching and adding Colors to a concrete mix involves selecting Pigments and incorporating them into the mix to achieve a consistent and desired hue. Here’s a step-by-step description of how it's typically done:
Selecting the Pigment Concrete can be colored using various types of pigments. Iron oxide pigments (most common) are used for earthy tones like red, brown, yellow, and black. Chromium oxide is used for green hues. Cobalt-based pigments are used for blue tones (less common and more expensive). Titanium dioxide is used to create white or to lighten other colors. Pigments come in powdered, granular, or liquid forms and are selected based on desired color intensity, cost, UV resistance, and compatibility with the cement type.
Color Matching. To achieve a specific color, sample testing is done first. Pigment proportions are adjusted, and trial batches are made to match the target color. A color chart or spectrophotometer may be used for precision. Factors considered include water-to-cement ratio, cement color (gray or white cement changes the base tone), aggregate color, and the finishing technique and curing method.
Mixing the Pigment Once the color is selected, the pigment is weighed accurately, usually as a percentage of the cement weight (typically 0.5% to 5%). Pigment is added to the dry mix of cement and aggregates to ensure even distribution before water is introduced. Consistency is key: mixing time and method must be standardized across batches to avoid color variations.
Pouring and Curing. The Colored Concrete is poured and finished like standard concrete. Uniform curing is essential—uneven moisture loss can affect color. Curing compounds or wet curing methods help retain even coloration.
Surface Treatments (Optional) To enhance or protect the color, Sealants may be applied after curing to enrich the color and protect against fading. Stains or dyes can be used post-cure to deepen or alter the hue if needed.