Spalling issues in concrete can have an adverse effect on the adhesion of concrete coatings. Spalling is when water enters the concrete and forces the surface to peel, pop up or flake off due to the expansion and contraction of the water within the concrete. This usually happens because there is moisture in the concrete. This can be common in below grade basements, wetter climates in the country or were the ground water table is higher. Excess moisture can arise from irrigation or sprinkler system also. A common issue in older slabs is no moisture vapor sheeting was applied under the concrete slab.
It’s important to identify the potential for this to happen so that you can explain the process to a customer, and hopefully avoid it happening, prior to installing an Epoxy coating.
If you do find a floor that is peeling or flaking, it’s crucial to identify whether it’s the concrete or the coating. Begin by scraping off a piece of the floor. Turn it over to see if there is concrete attached to the back of the coating. Typically, you will see some aggregate from the concrete still on the lifted coating. This is an indication that the concrete’s top layer of cement is what is breaking down and the coating itself did not fail. This is a sign of damage to the concrete due to moisture and spalling of the concrete.
Spalling can also occur when water freezes and thaws in the colder months, causing the concrete to expand and contract. That continuous cycle breaks down the concrete and it can fall apart. Chemicals such as the sodium chloride that is used to deice the roads in the winter months can also break down the concrete leaving the surface pitted and deteriorating. Another form of spalling can occur when exposure to salt in the air near the ocean breaks down the concrete.
Regardless of the reason for the spalling, it’s critical to explain it clearly and concisely to the customer if an issue occurs. When bidding on a job it’s important to recognize any issues with the concrete surface and explain the potential problems to the customer before applying an application. By educating the customer prior to starting a job if a problem occurs in the future they will be aware and a lot more understanding.