Cement laitance on concrete: what is it? A weak, milky or powdery coating of fine sand, lime, and cement dust that forms on the surface of concrete, but not only, is called cement laitance. Learn more about how and why it happens.
BRITTLENESS: The term “brittleness” in materials science refers to the tendency of a solid material to break into small pieces under the influence of stress or contact, especially friction. Thus, brittleness is a distinguishing characteristic of cement laitance. However, removing cement laitance due to this brittleness is not necessarily simple.
Cement laitance on concrete: what is it?
Water is an essential ingredient of a concrete mixture; full hydration of the cement component of the mixture is necessary for the concrete to cure well. Cement laitance will result from adding too much water to the mixture or insufficient curing.
When concrete is overwatered or allowed to cure too quickly without curing membranes or other appropriate curing techniques, these particles float to the surface. Excessive trolling can also cause these particles to rise.
To give concrete enough time to fully hydrate and reach maximum strength, proper concrete curing involves slowing the evaporation of water from freshly mixed concrete.
Covering freshly trowelled or formed concrete with wet burlap, wet sand, or a curing membrane (such as liquid wax emulsion) or at least plastic sheeting held at the sides to prevent wind movement are examples of excellent concrete curing practices.
Why remove laitance?
Adhesion to sound concrete determines the life of the coating. When applied over loose, friable cement laitance, the coating and laitance layer will delaminate under impact from trucks, forklifts, etc.
Can we paint over laitance?
The simple answer is no! Any laitance present will provide a weak, friable base for the coatings that will make it difficult to effectively adhere. Once you remove the laitance using diamond grinding, shot blasting, or other mechanical techniques, you can paint the resulting sound concrete surface without any issues.
What is the best method for removing laitance?
Mechanical techniques or the use of a specialised fluid, such as Betoff-BIO, are necessary to remove laitance from concrete surfaces. Diamond blasting and diamond grinding are reliable methods. These techniques will completely remove the weak, powdery layer, revealing the solid concrete underneath. This procedure is essential for any coatings or treatments on concrete to adhere properly and last longer.
Why is laitance a problem?
Laitance forms on the surface of fresh concrete—a thin layer of a weak, milky substance made up of fine sand, lime, and cement dust. Because it creates a brittle, fragile surface layer, it is problematic. This layer can reduce the overall strength and durability of a concrete structure by diminishing the adhesion of coatings or sealants applied to it, which may lead to flaking or chipping.
What effect does laitance have on concrete?
Concrete is susceptible to laitance because it weakens and degrades its surface. The life of the concrete surface is shortened by this weak layer’s susceptibility to wear and potentially improper adhesion of coatings or treatments. Laitance can cause concrete to deteriorate more quickly in high-traffic areas, requiring more regular maintenance and repairs.
What is the difference between laitance and efflorescence?
Concrete is susceptible to efflorescence and cement laitance, although their sources and symptoms differ. When water in concrete evaporates, a white, powdery layer of salts known as efflorescence forms on the surface, often visible to the naked eye. Conversely, cement laitance is a layer of a weak, milky substance consisting of fine particles and cement dust. Cement laitance compromises the structural integrity of the concrete surface, while efflorescence is primarily a cosmetic problem.
Which liquid is best for removing cement laitance?
In our product range, on the website betoff.eu you can purchase BETOFF-BIO liquid, which easily removes cement laitance from various surfaces, not only concrete.
