The approved plans specify 3,000 psi concrete for the foundation, but the delivery ticket in the driver hand describes a 2,500 psi mix, and no revision has been submitted to the department. What is the correct action?
- ARelease the placement, because 2,500 psi is the code minimum for structural concrete and is therefore acceptable in a footing of any size.
A code minimum is a floor, not a substitute for what the design calls for. Approved plans become the enforceable document once the permit issues, and a mix below the specified strength is a change to that document.
- BRelease the placement if the driver adds water at the site to improve the workability of the mix just before it is discharged.
Adding water at the site lowers strength rather than raising it, and the water content is fixed by the mix design in any case. This trades a documented shortfall for an undocumented one.
- CLet the pour proceed and then require core testing of the finished footing before any of the framing is allowed to start.
Core testing is a way to evaluate concrete already in place when there is no better option. Planning for it before the pour accepts a known deficiency and pushes the argument to the point where the fix costs the most.
- Hold the placement, because the mix delivered has to match the strength shown on the approved plans unless a revision is approved.
Why D is correct
Work has to be built in accordance with the approved documents, and a lower-strength mix than the plans specify is a deviation that requires approval before it is placed. Stopping the placement preserves every option: order the correct mix, or submit a revision for the building official to evaluate. Once the concrete is in the ground, the only verification left is destructive and the only remedy is expensive.
What this question is testing
Whether the candidate treats the approved construction documents as enforceable, and whether they act at the moment when action is cheap. It also tests knowing which verification tools belong before placement and which belong after, and rejecting field alterations that degrade the material.
On the job
Delivery tickets are the cheapest verification tool on a concrete job, and reading them takes thirty seconds. Mix-ups happen constantly when a plant is serving several jobs, and dispatch often sends the standard house mix regardless of what the plans said. Note the ticket number, the mix designation, the batch time, and the water added on site. If the strength is short, tell the superintendent before the truck discharges, because after that the conversation is about removal rather than about the next load.
Memory technique
Read the ticket before the chute drops: strength is easy to check and impossible to fix.
Exam tip
When plans and code minimums disagree, the more restrictive requirement on the approved documents controls the inspection.
Where to look it up
IRC Chapter 1 for construction in accordance with approved documents, and Chapter 4 for concrete material requirements and weathering-based strength tables.