A wall placement stops because the pump line plugs, and the leading edge begins to stiffen before the next lift can be placed. Which action best addresses the cold-joint risk?
Correct Answer
D) Create or treat a construction joint as directed by the specifications or engineer before continuing
Once concrete has stiffened enough to risk a cold joint, the crew should follow the specified construction-joint or surface-treatment procedure before continuing. Other choices: dry cement, extra vibration alone, and surface water do not create a properly bonded joint.
Why This Is the Correct Answer
Once concrete has stiffened enough to risk a cold joint, the crew should follow the specified construction-joint or surface-treatment procedure before continuing.
Why the Other Options Are Wrong
Option A: Cover the stiffened surface with dry cement and keep placing, leaving cold joint control unverified
Choice A gives Cover the stiffened surface with dry cement and keep placing. Its specific error: it leaves out the controlling Cold joint control result: Create or treat a construction joint as directed by the specifications or engineer before continuing.
Option B: Vibrate the next lift longer and ignore the elapsed time
Choice B (Vibrate the next lift longer and ignore the elapsed time) is rejected because the action skips the timing, documentation, or field-control step needed for Cold joint control.
Option C: Add water to the old concrete surface
In concrete work, Add water to the old concrete surface is the wrong selection for Cold joint control: it solves the wrong trade problem; the field result tied to Cold joint control is Create or treat a construction joint as directed by the specifications or engineer before continuing.
Memory Technique
Pair cold joint control with the real field trigger, then choose the response that produces Create or treat a construction joint as directed by the specifications or engineer before continuing.
Reference Hint
Open The Contractor's Guide to Quality Concrete Construction, 4th Ed., 2018; use the index entry or section for "Cold joints and construction joint treatment" to confirm that Once concrete has stiffened enough to risk a cold joint, the crew should follow the specified construction-joint or surface-treatment procedure before continuing.
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