ACI Concrete Finishing Defects & Troubleshooting Flashcards

What is the primary cause of scaling on concrete surfaces exposed to freeze-thaw cycles?

Answer: Using deicing chemicals on concrete with low air entrainment

Scaling is most often caused by applying deicing salts to concrete that lacks adequate air entrainment to withstand freeze-thaw cycles.

Surface dusting of a concrete floor is most commonly caused by which finishing error?

Answer: Troweling the surface while bleed water is still present

Troweling over bleed water dilutes the surface paste, resulting in a weak, dusty wearing surface.

Delamination of a concrete slab surface occurs because:

Answer: Air or bleed water becomes trapped beneath a prematurely sealed surface

When the surface is closed by troweling before underlying bleed water and air escape, they become trapped, creating a thin shell that later separates.

According to ACI, what finishing action most frequently leads to delamination in flatwork?

Answer: Finishing the surface before bleed water has evaporated

ACI states that prematurely closing the surface traps bleed water and air beneath the mortar-rich layer, causing delamination.

Which of the following best describes the ACI definition of surface scaling?

Answer: Peeling or flaking of the near-surface mortar layer

ACI defines scaling as the progressive loss of surface mortar or aggregate, exposing the underlying paste or coarse aggregate.

Plastic shrinkage cracking differs from drying shrinkage cracking primarily because it occurs:

Answer: Before the concrete has achieved initial set

Plastic shrinkage cracks form while concrete is still in a plastic state, when rapid evaporation exceeds the bleed rate.