A large concrete placement using the same mix is delivered across multiple days. What factor could contribute to color variation despite sameness of the mix?

A large concrete placement using the same mix is delivered across multiple days. What factor could contribute to color variation despite sameness of the mix?

• A. Differences in delivery timing
• B. Increased cement content
• C. Use of identical admixtures
• D. Constant humidity

Answer: (A)

Color variation in a large concrete placement with the same mix often comes from the conditions at the time of placement, especially the timing of delivery. Placing at different times of day exposes the concrete to different temperatures, humidity, and moisture loss rates. A batch poured in cooler, more humid conditions may cure with a different pigment shade and surface moisture than one placed in warmer, drier conditions. The surface moisture, bleed water, and how quickly moisture evaporates influence the final appearance, so even identical mixes can look different when delivered on different days or times. The other factors wouldn’t typically cause the same kind of day-to-day color change if the mix remains unchanged: increasing cement content would noticeably alter color, using the same admixtures shouldn’t create variation, and constant humidity would tend to stabilize color rather than cause variation.

Color variation in a large concrete placement with the same mix often comes from the conditions at the time of placement, especially the timing of delivery. Placing at different times of day exposes the concrete to different temperatures, humidity, and moisture loss rates. A batch poured in cooler, more humid conditions may cure with a different pigment shade and surface moisture than one placed in warmer, drier conditions. The surface moisture, bleed water, and how quickly moisture evaporates influence the final appearance, so even identical mixes can look different when delivered on different days or times.

The other factors wouldn’t typically cause the same kind of day-to-day color change if the mix remains unchanged: increasing cement content would noticeably alter color, using the same admixtures shouldn’t create variation, and constant humidity would tend to stabilize color rather than cause variation.