Views: 0 Author: Site Editor Publish Time: 2026-06-26 Origin: Site
Epoxy coated PC strand requires rigorous inspection to ensure its corrosion resistance and structural performance, especially in marine structures where defects can lead to premature failure. A systematic checklist helps engineers, inspectors, and contractors verify coating integrity, strand quality, and installation compliance before, during, and after prestressing. This prevents issues like pinholes, delamination, or mechanical damage that undermine service life.
This blog provides a comprehensive inspection checklist for epoxy coated PC strands, drawing from industry standards like ASTM A882, PCI guidelines, and practical field experience.
Start with paperwork to confirm traceability and compliance.
Verify mill test certificates (MTCs) for strand tensile strength (≥1860 MPa), low relaxation (≤2.5% at 1000 hours), and epoxy properties (fusion-bonded, 0.4–1.0 mm thick).
Check third-party coating reports for pinhole testing (NACE SP0188, <2/m), adhesion (>2000 psi per ASTM D4541), and thickness uniformity.
Confirm ASTM A882/A1007 or GB/T21073 compliance, including salt spray endurance (>3000 hours ASTM B117).
Review supplier qualifications (e.g., TJ Wasungen) and batch-specific cathodic disbondment results (ASTM G8).
Reject shipments without certified documentation.
Unreel samples from each coil for hands-on checks.
Inspect coating for uniformity: no blisters, cracks, chips, or discoloration; color should be consistent (green/black per spec).
Measure diameter (12.7/15.2/15.7 mm ±0.15 mm) and coating thickness (micrometer or eddy current, min 400 μm average).
Check for holidays/pinholes: run finger along 3–5 m length; no "hairy" feel or rust spots.
Examine ends and cut surfaces: clean, no exposed steel >2 mm; filler intact in interstices.
Verify packaging: coils on padded reels, dry storage, no contact with contaminants.
Document defects with photos; quarantine damaged reels.
Test mechanical integrity before use.
Lay 1 m sample flat: deviation <1/1000 of length (ASTM A370).
Check helical lay: outer wires snug, no gaps >0.5 mm; filler seals voids.
Inspect for kinks, birdcasting, or strand-within-strand from poor reeling.
Break test one sample per 100 tons: elongation ≥4%, no wire breaks outside coating.
Perform non-destructive checks on site.
Holiday detection: Use high-voltage wet sponge (900V) or DC holiday detector per NACE SP0188; zero holidays per 30 m.
Cross-cut adhesion: Score 1 mm grid (ASTM D3359); no flaking (>4B rating).
Bend test: 180° over 15D mandrel; no cracking or delamination.
Impact test: Drop 1 kg weight from 50 cm; no chipping >10% thickness.
Field kit costs < $500 but catches 90% of coating flaws.
Prevent damage during staging.
Storage: Elevated, shaded, covered; max 6 months exposure; RH <70%.
Handling: Padded gloves, slings; no dragging or dropping coils.
Sheave/radius check: Min 30x strand diameter for bends; inspect sheaves for burrs.
Duct compatibility: Plastic/metal ducts >1.5x strand OD; no sharp edges.
Monitor process stresses on coating.
Clean anchors/jaws: No debris; serrations intact.
Initial tension: Paint strands for slippage (<0.25% elongation).
Vibration check: No fretting or coating powdering during hold.
Post-detension: Inspect for strand marks, coating wear at abutments.
Concrete curing temp <65°C to avoid softening epoxy.
For bonded systems.
Strand placement: No kinks; coating intact after threading.
Grout: Cementitious, corrosion-inhibited; vacuum pressure >5 psi, no voids.
Anchorage seal: Epoxy patch ends 150 mm; smooth transition.
Stage | Key Checks | Acceptance Criteria | Tools/Methods | Frequency |
Documentation | MTCs, coating certs, compliance reports | ASTM A882 full pass | Review files | Per shipment |
Visual/Dimensional | Uniformity, thickness, ends, packaging | No defects; 400+ μm coating | Micrometer, magnifier | 10% of reels |
Mechanical | Straightness, lay, break test | <1/1000 dev; ≥4% elong | Ruler, tensile machine | 1 per 100 tons |
Coating Integrity | Holidays, adhesion, bend/impact | 0 holidays; >4B adhesion | Holiday detector, X-cut | All critical reels |
Handling/Storage | Condition, sheaves, ducts | No damage; >30D radius | Visual, radius gauge | Daily |
Pretensioning | Slippage, vibration, abutments | <0.25% slip; no wear | Paint, vibration monitor | Per bed |
Post-Install | Grout voids, anchorage seals | Full encapsulation | Boroscope, pressure gauge | 100% |
2 pinholes/30 m or rust under coating.
Coating thickness <350 μm or adhesion <1500 psi.
Mechanical damage >20% thickness or exposed steel.
Non-compliant docs or unapproved supplier.
Excessive slippage (>0.5%) or wire breakage.
Issue NCRs and notify suppliers (e.g., TJ Wasungen for replacements).
Annual checks for marine structures.
Visual: Cracks, blisters via borescope in ducts.
Ultrasonic thickness: Coating integrity.
Acoustic emission: Early wire breaks.
Half-cell potential: Corrosion activity <10 mV.
Train inspectors per PCI/PTI manuals; use calibrated tools. Partner with certified suppliers like TJ Wasungen for pre-inspected batches. Digital checklists (apps) ensure traceability.
Defective epoxy coated PC strand can halve service life from 75–100 years to 20–30 in saltwater exposure. Rigorous inspection safeguards investments, complies with codes, and avoids failures like those in early coastal bridges. Download this checklist for your next project and contact TJ Wasungen for compliant stock.
