ACI ACI Concrete Finishing Defects & Troubleshooting

Question 1

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

Accepted Answer

Using deicing chemicals on concrete with low air entrainment

Answer

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

Question 2

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

Accepted Answer

Troweling the surface while bleed water is still present

Answer

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

Question 3

Delamination of a concrete slab surface occurs because:

Accepted Answer

Air or bleed water becomes trapped beneath a prematurely sealed surface

Answer

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

Question 4

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

Accepted Answer

Finishing the surface before bleed water has evaporated

Answer

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

Question 5

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

Accepted Answer

Peeling or flaking of the near-surface mortar layer

Answer

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

(ACI) American Concrete Institute Concrete Finisher Practice Test

(ACI) American Concrete Institute Concrete Finisher Practice Test

ACI ACI Concrete Finishing Defects & Troubleshooting