Which statement best describes the relationship between air-entrained concrete and finishing passes in relation to delaminations?

Which statement best describes the relationship between air-entrained concrete and finishing passes in relation to delaminations?

• A. Delaminations are more likely with air-entrained concrete finished with multiple passes
• B. Delaminations are less likely with air-entrained concrete finished with multiple passes
• C. Delaminations occur equally regardless of air-entrainment
• D. Delaminations only occur with non-air-entrained concrete

Answer: (A)

Delamination is a separation between the hardened surface layer and the concrete beneath. Air-entrained concrete has many tiny air voids to improve freeze-thaw durability, but those voids can create a weaker surface layer if the surface is overworked during finishing. Finishing with multiple passes tends to rework the surface and can push excess cement paste to the surface, forming a thin laitance layer that doesn’t bond well to the underlying concrete. The combination of a surface weakened by laitance and the presence of near-surface air voids makes the top layer more prone to separating from the rest of the slab under load, shrinkage, or moisture changes. That’s why delaminations are more likely in air-entrained concrete finished with multiple passes. The other options either ignore the effect of surface finishing and air voids or incorrectly imply the risk only exists with non-air-entrained mixes.

Delamination is a separation between the hardened surface layer and the concrete beneath. Air-entrained concrete has many tiny air voids to improve freeze-thaw durability, but those voids can create a weaker surface layer if the surface is overworked during finishing. Finishing with multiple passes tends to rework the surface and can push excess cement paste to the surface, forming a thin laitance layer that doesn’t bond well to the underlying concrete. The combination of a surface weakened by laitance and the presence of near-surface air voids makes the top layer more prone to separating from the rest of the slab under load, shrinkage, or moisture changes. That’s why delaminations are more likely in air-entrained concrete finished with multiple passes. The other options either ignore the effect of surface finishing and air voids or incorrectly imply the risk only exists with non-air-entrained mixes.