Inspection and Testing of Prestressed Concrete Elements
Domain 5 tests the inspector's hold points and the tests that prove an element complies: concrete strength, steel properties, dimensions, camber, and grout.
Hold points
Before placement: forms, strand or duct layout, cover, anchorage hardware, spiral confinement, lifting inserts, and embed plates. At transfer or stressing: field-cured cylinder results and calibration records. After: camber, sweep, crack survey, dimensions, and grout records.
Tests and measurements
- Concrete cylinders per ASTM C31 and C39; field-cured for release.
- Strand and bar tests per ASTM A416 and ASTM A722.
- Grout fluidity and cube tests.
- Dimensional checks against shop drawings, including strand pattern and cover.
- Camber measured at a consistent time and support condition.
Worked example
A 60 ft precast beam has a specified camber of 2.5 in. Measured camber is 1.4 in., well outside a reasonable construction tolerance, and the beam is also 0.75 in. out of sweep. The inspector documents both, compares them to the approved shop drawing and tolerance, and reports to the design professional rather than accepting the member because it "looks fine."
Traps
- Signing off without current calibration records for jacks and gauges.
- Missing reduced cover at anchorages and embedded items.
- Accepting cracks without evaluating location, width, and cause.
- Measuring camber before the member is stable and fully detensioned.
- Treating a dimensional deviation as harmless without checking the approved tolerance.