A thin weak layer of fines and water is found on a slab surface where new topping must bond. In concrete work, that surface condition is best described as what?
Correct Answer
B) Laitance
Laitance is the weak surface layer of water, cement fines, and fine aggregate that can interfere with bond. Other choices: efflorescence is salt deposit, plastic shrinkage is a cracking mechanism, and entrained air is a designed air-void system.
Why This Is the Correct Answer
Laitance is the weak surface layer of water, cement fines, and fine aggregate that can interfere with bond.
Why the Other Options Are Wrong
Option A: Efflorescence
In concrete work, Efflorescence is the wrong selection for Laitance: it leaves out the controlling Laitance result: Laitance.
Option C: Plastic shrinkage reinforcement
Choice C gives Plastic shrinkage reinforcement. Its specific error: the option does not produce the required Laitance outcome, Laitance.
Option D: Entrained air
Choice D (Entrained air) is rejected because it points to Entrained air, but.
Memory Technique
Keep laitance as a cause-to-effect card with Laitance on the back.
Reference Hint
Open The Contractor's Guide to Quality Concrete Construction, 4th Ed., 2018; use the index entry or section for "Surface preparation and laitance" to confirm that Laitance is the weak surface layer of water, cement fines, and fine aggregate that can interfere with bond.
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