Flatwork Placement & Leveling 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 Flatwork Placement & Leveling flashcards as text
According to ACI 117, what is the standard flatness tolerance for a conventional concrete slab (not a defined-traffic floor) unless otherwise specified?
Answer: ±1/2 inch in 10 feet
ACI 117 specifies a standard tolerance of ±1/2 inch measured under a 10-foot straightedge for conventional flatwork unless more restrictive tolerances are specified.
Which placement method is preferred when placing concrete in a wall form that connects to a flatwork slab to prevent cold joints?
Answer: Pour wall and slab monolithically or with a construction joint treated with a bonding agent
Monolithic placement or a properly prepared construction joint with bonding agent ensures structural continuity between a wall and slab without a weak cold joint.
What is the primary risk of placing concrete on a subgrade that has been softened by rain or frost?
Answer: Uneven support causes differential settlement, leading to slab cracking
A soft or frost-affected subgrade provides uneven bearing, causing differential settlement under load and resulting in slab cracking over soft spots.
When using a laser screed on a large interior slab, what check must be performed before and periodically during the pour?
Answer: Verify the laser transmitter level and benchmark elevation to ensure grade accuracy
The laser transmitter must be confirmed level and set to the correct benchmark elevation; any drift in the reference plane causes the entire slab to be placed at the wrong grade.
What is the term for the deliberate upward pre-cambering of form supports to compensate for anticipated deflection of a suspended slab?
Answer: Camber
Camber is intentional upward curvature built into the formwork so that after loading and deflection, the slab achieves the design elevation and profile.
During screeding, what does a 'wet' area (low spot filled with paste) in an otherwise consistent surface most likely indicate?
Answer: A soft spot or void in the subgrade beneath that area
Paste-filled low spots often indicate soft subgrade areas where concrete has settled slightly, a warning sign of inadequate or non-uniform subgrade support.
What is the maximum recommended elapsed time between placing successive batches of concrete in a flatwork pour to avoid a cold joint?
Answer: No more than the initial setting time of the concrete, typically 30–60 minutes in warm weather
Successive placements must be made before the previously placed concrete reaches initial set (typically 30–60 minutes in warm weather) so vibration can integrate the layers.