![]() The loss of air entrainment can be avoided altogether by going with iron-oxide black for exterior concrete in icy climes. Davis Colors’ liquid form of carbon black is such a pigment, though the company’s powdered and granular forms of carbon black are not. And you’re going to have to spend time figuring out what the right dosage is going to be.”Īnother way to compensate for carbon black’s appetite for air entrainment agents is to use a carbon black pigment formulated specifically to leave entraining admixtures alone. However, air entraining agents aren’t free, so that may increase the cost of the concrete mixture. “If you increase your air entrainment dosage, you should be able to bring your air entrainment back up to the same level. “When you add carbon black your air content is going to decrease,” says Terry Collins, a concrete construction engineer with the Portland Cement Association. Some carbon black pigments absorb air entraining admixtures, rendering them useless. Air entraining admixtures, used to protect concrete against cracking in cold climates, introduce microscopic air bubbles that allow water molecules in the concrete to expand when freezing without causing damage. In freeze-thaw regions, the loss of air entrainment becomes an issue. “Black is easily one of our top five colors out of our 40 standard colors,” says Nick Paris, vice president of marketing for Davis Colors, the Los Angeles-based color manufacturer. In decorative concrete, integral black with a silver release is a popular combination. It’s sometimes used in highways and runways because black absorbs heat and discourages ice. It’s commonly used in driveways - and especially in gas stations - because it hides oil stains and grime. It can be mixed to darken other pigments, and it can be used alone to make light grays, dark grays or straight black. True or false? When using a black pigment to integrally color concrete, black is black and that’s that.īlack is widely used in the concrete industry. The large chips have both a smooth trowel and broom finish to show the impact surface texture can have on color appearance. The middle sample is made with 2 lbs/sack Iron Oxide Black and the darkest sample at right is made with 2 lbs/sack Carbon Black. The light colored sample at left is an uncolored reference. Colored concrete chips show the tint strength advantage of carbon black. ![]()
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