Construction Practice, Inspection, and Quality Control
This domain tests the field side of concrete: what to inspect, how often to test, which records prove compliance, and how to handle nonconformance without compromising the structure.
Submittals and hold points
Before placement, review mix designs, mill certificates, placing drawings, formwork and shoring design, and curing plans. Establish hold points for reinforcement and embed checks, cover verification and pre-placement sign-off. ACI 301 governs quality and ACI 318 governs structural acceptance.
Sampling and testing
Samples are taken per ASTM C172, not from the first discharge, and specimens are made and cured per ASTM C31 or C192. Typical minimum frequency is one strength set per day of placement, per 115 m3, or per 500 m2 of slab, whichever governs. Slump and air content are measured on each set; additional tests are required when appearance or consistency changes.
Hot and cold weather
ACI 305 limits fresh concrete temperature at placement, typically to about 35 degrees C, with cooling, ice or night placement. ACI 306 requires protection and heated enclosures once temperatures approach freezing, and prohibits placing on frozen subgrade.
Worked example
A 400 m3 slab pour at 115 m3 per set requires at least 4 strength sets, plus one set for each day and for each 500 m2 of surface. If one set falls below the acceptance limit, cores or additional testing are ordered before the engineer accepts the lot.
Traps
Sampling the first concrete from the chute; adding water at the site to restore slump without approval; accepting cylinders that were not standard cured; having no curing records when strength is questioned.