Many issues can delay the installation of concrete floors. While the most common problems are due to moisture. Some issues are also caused by poor substrate mixture ratio. One such difficulty that builders are plagued with during concrete floor construction is laitance.

Laitance removal is an important activity that contractors implement before installing the finishing touches over concrete floors. Unfortunately, laitance may not be detected right away. In some cases, laitance makes itself evident after high trafficking and repeated fluctuations in temperature. Laitance removal is integral as it ensures the proper adherence of coatings to the concrete.

Simply put, laitance is a term referring to the weak, siliceous material, and the easily-crumbled surface of the concrete. It consists of fine aggregates and cement that appear on the surface when too much water is added into the cement mixture. Laitance is also a product of excessive trowelling, moisture damage, and poor curing practices.

Laitance removal is integral surface preparation and should not be overlooked by building contractors.

Testing for laitance

There is no single technique to test for laitance. Most commonly, builders use a knife to scrape the floor to detect the presence of laitance. The excessive amount of white powder material on the surface automatically requires laitance removal. There are also testing devices used by contractors to detect the presence and thickness of laitance after concrete floor installation.

Here are some tried-and-tested methods of laitance removal:

  • Mechanical planing using milling machinery. The preferred method for the removal of thick laitance is mechanical planing. The aggressive function of planers quickly removes laitance from the floor’s surface. The cutting wheels of milling machines rotate to remove laitance in a fast and efficient manner.
  • Shot blasting. For bigger areas, the process of shot blasting or blasting is the preferred method of laitance removal. It removes laitance from a large surface area at a quick and steady pace. For high precision laitance removal, builders typically use hand-held grinding machines.
  • Acid etching. Acid etching efficiently removes laitance that produces a lightly-textured surface, although it carries a few disadvantages. It is a highly complicated procedure that requires professional help.
  • Floor sanding. Removing laitance from screed is best done using the floor sanding technique. Laitance removal is implemented 7 to 10 days after the screeding application. The method of using a sanding machine to remove laitance from the screed is known as abrading. Abrading involves the scouring of the surface to guarantee the removal of dust and other fine particles and to ensure that no laitance adheres to the screed flooring finish.

After sanding, all dust particles and aggregates are removed using an industrial-grade vacuum. Concrete and screed laitance removal ensures a durable and stable surface that is required for the installation of the final flooring finish.

With these in mind, it is important to implement laitance removal as it is a vital contributor to the success of concrete and screed flooring installation. Builders mustn’t skip this step in preparing concrete flooring for its final, decorative touches.