NICET - Highway Construction Inspection Practice Exam

What is laitance?

1. A protective layer for finished concrete

2. Weak surface layer from excessive vibration and water movement

3. A coating for preventing moisture entry

4. Concrete that has dried too quickly

The correct answer is: Weak surface layer from excessive vibration and water movement

Laitance refers to a weak surface layer that forms on fresh concrete as a result of excessive vibration and water movement. When concrete is mixed and placed, fine particles and cement paste can rise to the surface due to too much water or over-vibration, creating a layer that is not adequately bonded to the underlying concrete. This layer is typically made up of water, cement, and fine aggregate particles, which can weaken the surface and impact the durability and strength of the concrete structure. When laitance is present, it can significantly affect the performance of the concrete, leading to issues such as scaling, flaking, and reduced adhesion for subsequent surface treatments or coatings. For these reasons, it is crucial for construction inspectors and workers to recognize and address the formation of laitance to ensure the integrity of the concrete surface.