34th Annual Airports ConferenceHershey, PA

Preservation of Airport Infrastructure:

Using Correct Tools to Save Costs

Siva VenugopalanPrincipal EngineerSiva Corrosion Services (SCS)Siva@SivaCorrosion.comwww.SivaCorrosion.com

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), Inc.Siva@SivaCorrosion.comwww.SivaCorrosion.com

Thank You