34 th Annual Airports Conference Hershey, PA Preservation of Airport Infrastructure: Using Correct Tools to Save Costs Siva Venugopalan Principal Engineer Siva Corrosion Services (SCS)

We will discuss:  Quantifying material degradation, i.e. answering “how bad is bad?”  Recommending and designing solutions to extend service life cost effectively  Partnering with owners to solve problems In This Presentation

Electronic Current Ionic Current The CathodeThe Anode The Corrosion Reaction

 Dissimilar metals (galvanic corrosion)  Dissimilar electrolytes  Anode/cathode area ratio  Oxygen concentration  Stray current corrosion Factors Affecting Corrosion

Condition of Structure Cost of Maintenance Internal Damage First Visible Damage Critical Point Damage Accelerates Potential Failure Good: Preserve Fair: Extend Life Poor: Replace PS/PT: address here Reinforced concrete: address here Corrosion Cost Progression

Patching… and patching… and patching… Is there a more cost-effective option?

Temporary Piers

 How much concrete deterioration at present?  Chlorides at various depths?  Future penetration and effects of chlorides?  Active corrosion occurring? How quickly?  How much future damage?  Presence and progression of ASR? High risk of prescribing a poor solution without proper diagnosis… Evaluation

Boulevard – Structure Total Corrosion Potential

Boulevard – Structure Total Chloride Concentration Histogram

 Visible concrete damage – significant increase  Developed a concrete damage % for each element  Average recorded cover – moderate to high  Majority of potential tests – active corrosion  High chloride readings behind rebars  Near future concrete damage will result  Significant weakening of the structure within five years Conclusions

 Based on a unique methodology, developed recommendations for repair / replace / life extension  Concrete repairs on all bridges  ECE to lower chloride level near rebars and repolarize rebars  Sacrificial CP to maintain polarization of rebars  25-year additional life for structures  Sprayed Zinc Alloy – widely used, easy to apply Recommendations

 Why testing?  To understand where and how big the problems are  To properly design the solution  Owner will save $18,400,000  25-years additional life  Peace of mind Benefits

 Difficult to identify delaminations by sounding  GPR can rapidly identify delaminations before they become visible  GPR can identify reinforcement location/depth and member dimensions GPR

Rebars Surface and Rebar Reflections Surface Reflection

“V” Joints in Radargram “V” Joints

Diminished Reflections Delam AreaNo Delam

 Can find flaws not detectable by GPR and provide more information about those flaws  Well suited for flaw determination on structures with difficult access or multiple layers of materials (e.g. overlays) Impact Echo

Transient Response Sound Response Delaminated Response Delaminated vs. Sound Concrete

Pre-Stressed/Post-Tensioned Tank  Wastewater Tank built in 2001  Strands were greased and sheathed  Protection was previously believed to be sufficient

Pre-Stressed/Post-Tensioned Tank 6 Tendons run along the length of the walkway in each direction

Walkway Plan 82’-4” 51’-2”

Corrosion Strikes Strand corrodes, and after just 7 years… …fails and shoots out.

Inspection The strand was replaced and 12 additional strands were inspected

Inspection

Strand Anchorages

Inspection Based on testing, two strands were identified to have problems.

Strand Resistances Strands Removed

Solution  Two strands were removed  One failed during extraction  The other had significant section loss (would have failed soon had it not been removed)

Corroded Strand Before Cleaning…

Pitting and Section Loss After cleaning… After Cleaning

Pitting and Section Loss Strand only Seven Years Old

Pitting and Section Loss Strand only Seven Years Old

Corrosion of Pre-Stressed/ Post-Tensioned Structures  Corrosion causes localized wire breaks  Wire breaks cause increased stress on remaining strands  Sudden failure can occur if undetected and unmitigated (i.e. the strand shot out of the tank)

 Premature staining of a stainless steel roof coated with lead/tin alloy  Concerns that corrosion would continue, resulting in leaks  Expensive painting on underside Stainless Steel Roof Preservation

 Samples extracted from the roof for EDS & XPS analysis  Identified composition of corrosion product  Performed tests to determine corrosion properties of roofing material  Determined remaining life of roofing material before corrosion resulted in leaks Stainless Steel Roof Preservation

Parking Garage Rehabilitation  Design of new concrete mix for 40-year maintenance- free service life  Performed quality control testing  Identified areas of full depth removal  Evaluated bond strength, quality of epoxy coating, and defined repair procedures

Thermal Expansion Tank  Evaluated material compatibility and installation procedures  Performed NDT to identify the reasons for the leak  Recommended life extension solutions

Potable Water Pipe  Corrosion and mineral build-up led to problems  Quantified factors causing corrosion  Identified solutions to mitigate corrosive properties of water

Typical Solutions Galvanic CP For strands/I-beams Impressed Current CP For piers/piles Strands/I-beams Piers/Piles Anode Electrolyte Anode Rectifier

Rebar Mat Area of Interest

About SCS In-Depth Evaluation Life Extension Design Installation Inspection Service Life Extension:  Typically only 10-25% of replacement cost  Solutions for simple/ complex steel & concrete structures  Our Goal: Life Extension at the lowest overall cost

Siva Venugopalan Principal Engineer Siva Corrosion Services (SCS), Inc.