Challenge
A 54-inch reinforced concrete pipe was installed as part of a roadway project. Over time, concerns arose about its condition and performance. A full evaluation was required to determine whether the pipe was structurally sound, identify defects, and recommend any necessary rehabilitation or repairs.
Technical Analysis
Back Municipal Consulting conducted a thorough assessment that included pipe design review, visual inspection, and structural analysis.
Key findings:
- Exposed Stirrup Holding Assembly Wire – Found in 35 of the 72 pipe sections, totaling 179 locations. Wires were exposed primarily at the 6 o’clock position, likely due to insufficient concrete cover during manufacturing.
- Exposed Structural Steel – Two locations showed exposed reinforcement near joints, likely caused by installation impact damage.
- Voids – Significant voiding was identified in one section, likely due to manufacturing defects.
- Patches – 26 sections contained previous mortar repairs, all in sound condition.
- Surface Deterioration – Minor abrasion (<0.025”) observed along invert, likely from initial abrasive flows.
- Rust Lines and Spots – 639 occurrences recorded, cosmetic only, with no exposed reinforcement.
- Cracks – One surface crack observed in a single section, no deflection measured.
Despite these imperfections, the overall pipe structure was determined to be sound, with no signs of deflection, joint failure, or loss of structural integrity.
Recommendations
Repairs were advised to ensure long-term service life and prevent deterioration:
- Address 179 areas of exposed stirrup wire.
- Repair two exposed steel bars at joints.
- Fill voids in Section 26.
- Repair surface crack in Section 29.
BMC recommended using a 100% solids epoxy compound (CPP) for all repairs. This product provided superior strength to the existing concrete, ensuring durable coverage for exposed steel, filling voids, and crack sealing.
Outcome & Lessons Learned
The evaluation confirmed that the pipe was structurally sound overall, but highlighted manufacturing quality control issues (insufficient cover over reinforcement, voids) and the importance of thorough inspection prior to and after installation.
Industry lessons include:
- Ensure minimum concrete cover is maintained during manufacturing.
- Document and repair imperfections prior to service.
- Use durable epoxy-based materials for patching and rehabilitation.
- Conduct comprehensive visual and photographic inspections to guide asset management.
BMC’s Role
BMC provided a complete engineering evaluation and repair strategy, combining design review, detailed inspection, and material recommendations. By documenting over 300 photographs, 72 inspection sheets, and technical analysis, BMC ensured the owner had a defensible, standards-based assessment to guide rehabilitation decisions.
