34 th annual airports conference hershey, pa preservation of airport infrastructure: using correct...
TRANSCRIPT
34th Annual Airports ConferenceHershey, PA
Preservation of Airport Infrastructure:
Using Correct Tools to Save Costs
Siva VenugopalanPrincipal EngineerSiva Corrosion Services (SCS)[email protected]
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
Cos
t of M
aint
enan
ce
InternalDamage
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 Piers11 Bridges in Southeast U.S.
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
0.25 0.5 0.7
5 11.2
5 1.5 1.75 2
2.25 2.5 2.7
5 33.2
5 3.5 3.75 4
4.25 4.5 4.7
5 5M
ore
0
20
40
60
80
100
120
Boulevard - Structure TotalRebar Cover Histogram
Rebar Cover (Inches to Top of Rebar)
Fre
quen
cy (#
of S
ampl
es)
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
-750
-700
-650
-600
-550
-500
-450
-400
-350
-300
-250
-200
-150
-100
-50
Boulevard - Structure TotalCorrosion Potential
Corrosion Threshold
Corrosion Potential
Cumulative Frequency
Half-
Cell
Pote
ntial
(mV)
90% Probability of Active Corrosion
Boulevard – Structure Total Corrosion Potential
0.005
0.015
0.025
0.035
0.045
0.055
0.065
0.075
0.085
0.095
0.105
0.115
0.125
Mor
e0
1
2
3
4
5
6
7
Surface Sample
Rebar Sample
Behind Rebar Sample
Chloride Content (% Wt. Concrete)
Fre
quen
cy (#
of S
ampl
es)
Active CorrosionT
hres
hold
Boulevard - Structure TotalChloride Concentration HistogramBoulevard – Structure Total Chloride
Concentration Histogram
Visible concrete damage – significant increaseDeveloped a concrete damage % for each
elementAverage recorded cover – moderate to highMajority of potential tests – active corrosionHigh chloride readings behind rebarsNear future concrete damage will resultSignificant weakening of the structure within
five years
Conclusions
Based on a unique methodology, developed recommendations for repair / replace / life extension
Concrete repairs on all bridgesECE to lower chloride level near rebars and
repolarize rebarsSacrificial CP to maintain polarization of rebars25-year additional life for structuresSprayed Zinc Alloy – widely used, easy to apply
Recommendations
S. No.
StructureReplacement
costRepair cost
Cost Savings
Repair cost/ Replacement
cost, %
1 Boulevard $1,931,202 $402,300 $1,528,902 21%
2 Hermitage Road $3,240,312 $619,720 $2,620,592 19%
3 Laburnum Avenue $1,730,258 $380,480 $1,349,778 22%
4 Lombardy/CSX $5,821,420 $2,019,420 $3,802,000 35%
5 Overbrook Road $1,147,005 $312,240 $834,765 27%
6 Ramp-A $926,000 $146,440 $779,560 16%
7 Robin Hood Road $1,877,817 $568,560 $1,309,257 30%
8 Sherwood Avenue $1,595,045 $397,700 $1,197,345 25%
9 Upham Brook Run $2,287,719 $429,620 $1,858,099 19%
10 Westwood Avenue $3,592,000 $402,440 $3,189,560 11%
Total $24,148,778 $5,678,920 $18,469,858 24%
Why testing? To understand where and how big the problems areTo properly design the solutionOwner will save $18,400,000 25-years additional lifePeace 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 Area No 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
Inspection
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 CPFor strands/I-beams
Impressed Current CPFor piers/piles
Strands/I-beams Piers/Piles
Anode
AnodeElectrolyte Electrolyte
Anode
Anode
Rectifier
Rebar MatArea of Interest
About SCS
In-Depth Evaluation
Life Extension Design
Installation Inspection
Service Life Extension:Typically only 10-25% of
replacement costSolutions for simple/
complex steel & concrete structures
Our Goal: Life Extension at the lowest overall cost
Closing:About SCS
Questions?
Siva VenugopalanPrincipal Engineer
Siva Corrosion Services (SCS), [email protected]
Thank You