Removing Laitance from Screed
A screed is a layer of material applied to a floor surface in the semi-liquid form to level it out and create a smooth, even surface. Although there are several types of screed for a wide variety of surfaces, liquid screed has become the most reputed way for many years. It’s affordable, tough, easy to lay and apply, and dries rapidly.
All the liquid screed’s reputation lies in its composition; the calcium sulphate replaces the cement-based binder plus gives a better finish. Moreover, the whole drying-up process takes 3-7 days to create a rigid layer of crystalline Gypsum. But sometimes, an uneven layer called laitance forms over the surface that must be removed.
What is Laitance?
Laitance is a term used to describe a thin layer of weak, powdery material that forms on the surface of freshly poured or cured concrete or screed. It comprises cement particles, sand, and other fine materials that rise to the surface during the screeding or curing.
It showcases an excessive amount of moisture rising to the surface, potentially hindering the typical fast-drying process of liquid screed. If not removed, laitance can interfere with the bond between the screed and any subsequent coatings or finishes applied on top of it. It can also weaken the durability of the screed, potentially leading to cracking or spalling over time.
Therefore, removing laitance from screed by some professional workers is essential. For your information, experts use several methods to remove the laitance from the screed. Read the following section of this in-detail guide to learn about all those tactics.
How Experts Remove Laitance? Methods Explained
Multiple methods are used to remove laitance from the screed depending upon the area that needs to be screed, what the floor will be used for, and a few other factors. The following are those methods for removing laitance from the screed.
- Floor Sanding
- Shot Blasting
- Dust-free Grit Blasting
- Concrete Planning
Floor sanding is a mechanical method for removing laitance from a screeded surface for one week to ten days. It involves using a floor sander, or ‘abrading’, a large machine that uses abrasive sandpaper discs to remove the top layer of the screed surface.
The floor sander rotates the sandpaper discs at high speed, which abrades the surface and removes the laitance buildup; this is why floor sanding is sometimes called ‘abrading’. The sander typically uses a series of progressively finer sandpaper grits to achieve a smooth, even finish on the screed surface.
The floor sanding method effectively removes laitance, dust, and fine particles from a screeded surface. It can quickly and efficiently remove the powdery layer and create a rough, textured surface suitable for applying coatings or finishes.
In the shot blasting method, a shot blasting machine uses steel shot or grit to fire or blast the screed surface at high velocity to remove laitance mechanically. In other words, the shot blasting process works by propelling the abrasive particles onto the surface of the screen, which abrades and removes the laitance buildup.
It is an effective method for removing laitance from a very large screeded surface. This is because it quickly and efficiently removes the powdery layer and creates a rough, textured surface suitable for finishes. Moreover, since it’s a dry method, floor laying can be done in the same room where the process is completed.
Dust-free Grit Blasting
Dust-free grit blasting is a dry method for removing laitance from a screeded surface; you can simultaneously remove laitance while working on the already grit-blasted areas. This method involves using a specialized machine that blasts the surface with abrasive particles, such as sand or grit, to remove the laitance buildup.
If scrabbing isn’t a suitable way to remove laitance, you can go for dust-free grit blasting. The grit-blasting machines use a vacuum system to collect and remove the debris generated during the process, reducing the dust and airborne particles created. Therefore, it’s a great way to work indoors and outdoors.
Scabbing is another method for removing the laitance from the screed and preparing the floor for the final finishes. In this method, a scrabbler machine is used to roughen the substrate or the flooring surface using carbide-tipped pistons. Remember, this process is noisy and isn’t suitable for working indoors.
On the other hand, it’s a great way for outdoor projects, including pathways in your garden or bigger concrete roads with bigger machines; this method is used where the concrete layer is more than 10mm thick. Moreover, a lot of dust could be there on the site, so it’s essential to take proper safety measures.