Prestressing Materials and Components
Domain 1 of the ICC Prestressed Concrete Special Inspector exam covers the physical materials that make up a prestressed element and the accessories that anchor and protect the prestressing steel. Questions focus on identifying products, checking mill certificates against the specification, and recognizing matched anchorage systems.
Steel products and their standards
- Seven-wire strand: ASTM A416. Grade 270 (1,860 MPa) low-relaxation is the default in building work; Grade 250 also exists. Strand is identified by diameter, grade, coating, and relaxation class.
- Uncoated wire: ASTM A421.
- High-strength bar: ASTM A722, commonly 150 ksi, with threaded or upset ends.
- Epoxy-coated strand: ASTM A886.
Hardware, ducts, and accessories
Anchor heads and bearing plates, two- or three-piece wedges, barrels, couplers, trumpets, spiral confinement, ducts (galvanized steel, corrugated metal, or HDPE), grout caps, and vents. Confinement steel behind an anchorage resists the burst zone and is required by the system supplier. Components are a matched system - never substitute wedges or plates from another supplier.
Worked example
A coil of 0.6 in. Grade 270 strand arrives with a certificate showing a breaking load of 57.2 kip. Nominal area is 0.217 in², so the ASTM A416 minimum is 270 ksi × 0.217 in² = 58.6 kip. The certificate is below the minimum; reject the lot, quarantine the coil, and record the heat number.
Traps
- Assuming "Grade 270" on the label proves compliance - check the actual test values and relaxation class.
- Losing heat-number traceability when coils are moved or mixed.
- Accepting kinked, bent, or pitted strand.
- Overlooking anchorage confinement steel because it is embedded and easy to miss.