Q: We've just started doing decorative concrete work and want to know how soon to power-wash and seal a colored surface after concrete placement. One person told me to wait a week before power washing, otherwise the high-pressure water might damage the concrete. Another person told me to power wash the concrete the day after it's placed. What's the correct timing for this operation?
A: We checked with two experienced decorative concrete contractors and both recommended washing the surface the day after placement. One says he power washes at that time because if he waits too long before washing and sealing, the concrete can get stained by dirt, leaves, or other materials. The other contractor says he used to power wash after 24 hours, unless the temperature was low or some other factor might have prevented the concrete from gaining enough strength to resist any surface damage caused by the high-pressure water. He now uses a mild acid wash the day after concrete placement and then seals the concrete after rinsing the surface and allowing it to dry.