Four types of color metering systems offer advantages and disadvantages.
Premixed color (or liquid) systems are easy to install, most systems offer an easy-entry recipe computer program, and their slurries disperse quickly. Disadvantages include a relatively high cost and the necessity of re-agitating premixed slurry prior to use.
Dry-wet color metering systems combine powder or granular pigment with water, creating slurry. Virtually any earth tone color can be produced. The short cycle time of dry-wet systems enables a single station to serve multiple production lines. These systems' primary disadvantage is that the extra water introduced may be undesirable in dry-cast mixes, and the extra water affects the water-cement ratio.
Granular color metering systems use no water. Binders combine billions of pigment particles into microbeads. The binders break down in the mixer, releasing the pigment particles. These systems yield labor savings due to a bulk sack delivery method and a fully automated, closed-loop operation. Granules' flowability offers slightly higher metering accuracy. The process does not affect water-cement ratios. Additionally, granules are less dusty than dry pigments. However, granules are typically more expensive than other types of pigment and may not be available in some markets.
Color powder metering systems use the lowest-cost pigment available and add no additional water. The primary disadvantage is difficult installation.
The article also includes key control factors in a successful color metering operation.
keywords: color, pigment, granular, powder