Many issues can plague concrete floor construction. While most of the problems are typically attributed to moisture, some difficulties trace back to a poor substrate and mixture proportion. One example of a common problem with concrete floors is laitance. A layer of laitance on concrete will prevent paint and other finishing compounds from adhering.
Contractors understand the importance of removing laitance before applying any finishing touches over concrete. Unfortunately, laitance may not appear instantly. By constant exposure to traffic as well as temperature changes, the layer of laitance will eventually appear. Without adequate laitance removal, it will be costly to repair and re-apply coating over the concrete once the laitance appears.
What causes laitance?
Its powdery and crumbly appearance characterises laitance. It appears as a layer of concrete and fine particles forming on top of concrete. The primary cause of laitance is excess water in the concrete mix. Other causes include insufficient curing, overworking the concrete mix, and rain.
Unfortunately, laitance almost always appears on new concrete. However, even old concrete surfaces may be prone to laitance. At first glance, laitance may seem like nothing more than a layer of dust. But not removing laitance has significant consequences.
Testing for laitance
There is no need to employ highly technical methods to test for laitance. You can use a knife to scrape the floor. If there is an excessive amount of white powdery material, you need laitance removal. If you want to know laitance thickness, score the surface until you reach the aggregate. If you want something more accurate, there are testing devices that professionals use.
How do you remove laitance?
There are different methods available for removing laitance. Choosing a method depends on the surface area, how much laitance needs removal, laitance thickness, and the amount of detail required for the project.
For thick laitance, a mechanical planning machine is the preferred method. These planers, otherwise known as milling machines, can quickly remove laitance because of the device’s more aggressive function. The machine’s cutting wheels rotate to chip away at the laitance on the surface efficiently.
For more extensive work areas, grinding or shot blasting are preferred methods. Since it usually takes time to remove all the laitance from the surface, you will need a machine that can get the job done faster. With a grinding machine or a shot blaster, you can cover a large area in a single go. If precision is a priority, try a hand-held grinding machine. However, it will take you longer; hence, it is best used only for smaller areas.
Another method used in removing laitance is acid etching. Although using acid is useful to a certain extent, it is a complicated process and involves some hazard.
Choosing the right method to remove laitance dramatically impacts productivity. For commercial projects, it is best to use heavy-duty machines. For residential projects, you may use smaller devices that guarantee greater precision.
Laitance removal is a critical step in preparing a concrete floor for decorative coating. It is vital never to skip this step to ensure the quality of your flooring.