Concrete laitance refers to the layer of weak particles and cement that forms on the surface resulting from too much moisture. Laitance increases when you over manipulate or overwork concrete. Moreover, improper or insufficient curing also leads to more laitance forming on the surface. In general, you will observe that laitance can be coarse or fine, depending on the underlying factors.
Different methods of concrete laitance removal
Removing laitance is essential because leaving it on the surface prevents other materials from adequately adhering to the concrete. The technique used in laitance removal will depend on the environment as well as the purpose of the concrete surface.
- Shot blasting. It is an efficient and fast technique used when laitance removal involves a large area. The method makes use of equipment that fires abrasive materials over the concrete. Since it is a dry method, it is ideal when there is continuous floor-laying work ongoing in other parts of the building.
- Mechanical planning. A machine with rotating cutters is used to remove laitance. This method, in particular, is best when there is a thick layer that needs to be removed. Since it is mechanical, the process is deemed efficient and fast.
- Scrabbling. Using a floor scrabbling machine is considered heavy-duty, but the device is quite noisy. It also takes time to finish the job, and the work area can get quite dirty and dusty. If using a scrabbler to remove laitance, it is essential to wear protective clothing and a mask to avoid inhaling the dust particles.
- Grinding. If the area is small, you can use a grinding machine to remove laitance. A hand-held device gives you more control and also enhances precision.
- Acid etching. This method is best used for thin laitance and non-porous surfaces. Acid applied on the surface will quickly breakdown the laitance, which makes this method very effective. However, you need to take extra precautions in using this method. It is recommended to use acid etching only when all other methods are not applicable.
- Abrading. You can use abrasive paper to remove concrete laitance, but this method is quite limited. You can only work on small areas at a time, which makes the entire process time-consuming.
Indeed, choosing a removal method is vital to efficiency. Nonetheless, it is still best to compare the pros and cons of each approach to decide which is best for the project you are working on.
What is efflorescence, and how does it differ from laitance?
Some people confuse efflorescence and laitance because of the similar appearance. However, efflorescence is different from laitance, as discussed in the following comparison.
- The cause of efflorescence is soluble salts present in concrete, while laitance forms when the concrete mix has too much moisture.
- You can avoid efflorescence by buying materials that do not contain salts. On the other hand, laitance is prevented by controlling the water content of a concrete mix.
- In removing efflorescence, you can use pressurised water, acid, or a sandblaster.
In conclusion, both efflorescence and laitance affect the quality of a concrete surface. It is vital to use the recommended method of removal to preserve the structural integrity of the concrete surface.