Random cracks appeared on yesterday's slab panel before the sawcut crew arrived. For the next panel, how should contraction-joint timing be controlled?
Correct Answer
D) Saw as soon as the concrete can support cutting without raveling, within the specified early-cut window
Contraction joints need to be cut early enough to create a weakened plane before random shrinkage cracking, but not so early that edges ravel. Other choices: waiting days, waiting until curing ends, or omitting joints allows uncontrolled cracking.
Why This Is the Correct Answer
Contraction joints need to be cut early enough to create a weakened plane before random shrinkage cracking, but not so early that edges ravel.
Why the Other Options Are Wrong
Option A: The crew should wait at least two days so the concrete reaches more strength
Choice A gives Wait at least two days so the concrete reaches more strength. Its specific error: it leaves the work at an informal or incomplete stage, while Sawcut timing requires Saw as soon as the concrete can support cutting without raveling, within the specified early-cut.
Option B: The crew should cut only after all curing is complete
Choice B (Cut only after all curing is complete) is rejected because the option delays or omits the controlling step.
Option C: Skip joints because random cracks already relieved the stress
In concrete work, Skip joints because random cracks already relieved the stress is the wrong selection for Sawcut timing: the action skips the timing, documentation, or field-control step needed for Sawcut timing.
Memory Technique
Tag the scene with sawcut timing: wrong actor or wrong timing means the fix is not Saw as soon as the concrete can support cutting without raveling, within the specified early-cut window.
Reference Hint
Open The Contractor's Guide to Quality Concrete Construction, 4th Ed., 2018; use the index entry or section for "Slab contraction joint timing" to confirm that Contraction joints need to be cut early enough to create a weakened plane before random shrinkage cracking, but not so early that edges ravel.
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