Concrete samples mishandled, board orders extra breaks and contingency testing

The owner's representative reported a procedural error by the materials‑testing vendor that left concrete cylinder samples in an on‑site cooler for four days rather than retrieving them the next day, possibly exposing the specimens to temperatures above the 80°F threshold and depressing 7‑day strength readings. “There were a couple instances where the technician left the cylinders in the cooler on‑site for 4 days instead of picking them up the next day,” the owner’s representative said.

The board heard that, although some 7‑day results were lower than expected, all results remained within criteria required to set structural steel. The project team agreed to break spare cylinders earlier than planned this week to confirm strength and to perform nondestructive testing (Windsor probe) on foundations if any sample fails to meet the 75% threshold required to start steel erection. The structural engineer and the concrete supplier participated in an on‑site meeting and the team assigned the testing vendor (IMTL) responsibility to correct the process and, if necessary, bear the cost of any accelerated testing incurred because of their handling error.

Board members emphasized documenting engineer‑directed acceptance procedures and ensuring the process is recorded in the project file. Contractors and the owner’s rep said the chance of failing to reach the required strength is remote because parallel sampling by the concrete supplier and spare cylinders give redundancy, but the team agreed the nondestructive test option would be used if any discrepancy remains.