Surface Preparation & Finishing Techniques Flashcards
7 cards from real ACI practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Surface Preparation & Finishing Techniques flashcards as text
When finishing concrete in hot weather, which measure helps prevent rapid surface drying?
Answer: Using evaporation retarder (aliphatic alcohol spray) on the surface
Aliphatic alcohol-based evaporation retarders form a temporary film that slows moisture loss from the concrete surface during finishing.
What is the primary purpose of a control joint in a concrete slab?
Answer: To create a weakened plane that directs cracking to a predetermined location
Control joints create a weakened plane so that shrinkage cracks occur along the joint rather than randomly across the slab.
What minimum depth should a hand-tooled control joint be cut to effectively control cracking in a 5-inch slab?
Answer: 1.25 inches (one-quarter of slab thickness)
ACI recommends control joints be cut to a minimum depth of one-quarter of the slab thickness to create an effective weakened plane.
Which type of trowel produces the smoothest, most dense finished surface on interior concrete floors?
Answer: Steel trowel
A steel trowel, especially on successive passes, compresses and densifies the surface mortar to produce a hard, smooth finish.
What finishing defect appears as a network of shallow cracks resembling a map or spider web on a concrete surface?
Answer: Crazing
Crazing is a pattern of fine surface cracks caused by rapid drying, over-troweling, or dusting dry cement onto the surface.
Why should dry cement or sand NEVER be sprinkled onto bleed water on a concrete surface?
Answer: It increases the water-cement ratio and weakens the surface
Adding dry cement to absorb bleed water raises the water-cement ratio at the surface, resulting in a weak, dusting layer prone to scaling.
A stamped concrete finish is best applied:
Answer: While the concrete is in a plastic state, after bull floating and color hardener application
Stamps are pressed into the surface after the concrete has been colored and reached the right consistency — firm enough to hold the pattern but still plastic.