Adding pigment to create integral color in Cement follows a different rule than for other coatings. The maximum ratio of pigment for any cementitious product is 10% to the weight of the cement binder. Oxides will have the strongest tinting strength, and white cement will produce a different effect than a gray cement base. Aggregate color will affect the shade as well. Other factors that can affect color are the type of cementitious materials, water-cement ratio and stiffness of mortar when tooling. Creating samples is recommended to determine all these factors. The same integral color rules apply for other forms of decorative concrete such as molded concrete for furniture, countertops and statuary.
To add integral color to your concrete or stucco mix, calculate your proportion by the weight of the dry cement, before the addition of water and aggregate. If lime is used its weight is also included in the calculation. The ratio cannot exceed 10%. Pigment color is added directly into the concrete mixer, without any additional water. The use of an additional concrete bonding agent is recommended but optional. Controls at a job site must be in place to ensure that color is added in the correct weight ratio, mixed properly, that ingredients are not contaminated and remain consistent.
Briefly mix together the listed amounts in this order, (mechanical mixing is recommended):
- 75% of the water
- 50% of the sand
- 100% Pigment ratio
- 100% Cement (and lime if applicable)
- 100% of any additional bonding agent (if used)
Then add the remainder of the water and sand and mix to a workable consistency. Once the proper consistency has been reached, the batch must then be mixed for an additional full 5 minutes. Mix only the amount of mortar to be worked immediately. If additional water is added to mortar that has become stiff, the color will be affected.