The 28 day rule is used painting and concrete contractors as a rule of thumb to time the proper curing of a concrete slab. Coating or painting the concrete too early in its life cycle spells disaster for the coating and is a hit to the pocketbook as well. By following the 28 day rule, your painting contractor is making sure that the concrete is ready hold a coating.
After curing for 28 days, most types of concrete can be prepped for painting. Although the preparation process may vary from product to product, prep work is absolutely vital to the finished look of the concrete coating. This bears repeating: Prep work is absolutely vital to the finished look. No exceptions.
As part of the curing process, water reacts with the cement and the aggregate mix. Sometimes, the proper water to cement ratio is maintained by coating the fresh concrete with a sealer, which prevents water from leaving the drying concrete too rapidly. While this sealer is necessary to create good concrete, the sealer often interferes with paint’s ability to effectively bond with the surface.
Your painting contractor will remove any sealers before painting new concrete. Once cleaned the surface is further prepared by acid washing or shot blasting. For some concrete slabs, a water and salt blocking layer may be applied to protect the finish from seepage from underneath the concrete.
After the concrete has been thoroughly cleaned and dried, your contractor lays down the first coats that will become a durable and attractive concrete floor finish.
Have a great weekend.