What does laitance refer to in concrete?

Laitance specifically refers to a weak surface layer that develops on freshly poured concrete due to the upward movement of water and finer particles of cement during the curing process. This phenomenon occurs when water rises to the surface, bringing with it unbonded cement particles, which then form a soft, powdery film on top of the concrete. This weak layer can compromise the strength and adhesion of any subsequent treatments or coatings applied to the surface, making it crucial to remove laitance before further processing.

Understanding laitance is essential for coatings inspectors, as this condition can significantly affect the performance of coatings and the longevity of the concrete surface. Proper assessment and preparation of the concrete surface, including the removal of any laitance, are critical steps to ensure successful adhesion and the durability of protective coatings.