Q: Besides changing the color, does adding pigment to concrete have any other effects on its properties that a contractor should be aware of?

A: Provisions in ASTM C979-10, “Standard Specification for Pigments for Integrally Colored Concrete,” allow the possibility pigments might alter two properties that would affect your work as a contractor—setting time and air content. A pigment meeting this standard can accelerate initial or final setup to one hour or retard it by as much as one and a half hours, which could easily impact your timing to place, consolidate, and finish integrally colored concrete. You should check with the ready-mix producer to find out whether and how the pigment in a particular mixture will affect its time of set.As for air content, the standard allows for a pigment to change the air content of a concrete mixture by no more than 1%, compared to an unpigmented mix, so it’s a good idea to find out whether you’ll need to adjust the amount of air entrainment to ensure a desirable air content for the project.Keep in mind, however, that these allowances are based on the maximum dosage prescribed for pigments, and the actual dosage and effects are likely to be less.