Corrosion Assessments for Parking Structures

Corrosion Assessments for Parking Structures

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CONCRETE PRESERVATION ALLIANCE

The Concrete Preservation Alliance is a growing coalition of organizations committed to advancing best practices in the field of concrete preservation and infrastructure renewal.

Working together to promote education and awareness of concrete repair industry standards, new and innovative corrosion prevention technologies and sustainable construction practices.

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OUR MEMBERS

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WESAVESTRUCTURES.INFO

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Dr. Brian Pailes, Ph.D., P.E., NACE Specialist

Brian is the Principal Engineer with VCS, a professional engineer and certified NACE Cathodic Protection Specialist (CP4).

Brian has extensive experience in the field of nondestructive evaluation (NDE), material testing, structural evaluation and corrosion assessment of reinforced concrete structures.

He earned a Ph.D. in Civil Engineering from Rutgers University, an M.S. in Civil Engineering from the University of Virginia and a B.S. in Civil Engineering from Northeastern University. Brian has also obtained a Graduate Certificate in Engineering Geophysics.

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Corrosion Assessments for Parking Structures

• Professional services to extend the service life of parking and building structures

• Understanding the cause and effect of reinforcing steel corrosion in concrete

• Quantifying the magnitude and extent of corrosion risk.

• Many destructive and non-destructive test methods for assessing corrosion risk.

What is really happening in the concrete?

• Large Near surface Delamination

• Extent of delamination beyond what sounding can pick up

• Corrosion is active but has not formed enough iron oxide to create significant cracking

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Corrosion

• Electrochemical reaction requires:

• Moisture• Electrolyte – concrete• Metallic path – steel

• Anode• Where rust is formed

• Cathode• No section loss

• Chloride ions diffuse into concrete and destroy steel’s passive layer

• Source of chlorides• Marine environments• De-icing salts• Chemical/processing plants• Cast into concrete

• Chlorides are not consumed in corrosion reaction, therefore, once threshold concentration reached, corrosion can occur unabated

Chloride Induced

•Carbon dioxide permeates into concrete

•Reduces pH of concrete• CO2 reacts with free lime, Ca(OH) 2,

resulting in CaCO3 and H2O•Reduced pH de-passivates steel•Often seen when

• Concrete permeability is high• Industrial sites• Very old structures – carbonation is a

result of time and exposure

Carbonation

Corrosion Induced Damage

0 1 2 3 4 5 6 7Relative Size

Fe

FeO

Fe3O4

Fe(OH)2

Fe(OH)3*3H2O

Pilling-Bedworth Ratio

Corrosion Induced Damage

•Conventional mild reinforcing bar• Typically damage to concrete becomes significant

and observable prior to severe steel section loss •High Strength Tendons

• Minor section loss of steel can have significant effect on strength

• Steel can have significant section loss without significant concrete damage

How can we better understand these

deterioration conditions?

REBAR CORROSION DELAMINATION SPALLING

IMPACT ECHO

CHAIN DRAG

VISUAL INSPECTION

BRID

GE

DEC

K C

ON

DIT

ION

TIME

HALF-CELL POTENTIAL

ELECTRICAL RESISTIVITY

GROUND PENETRATING RADAR

CHLORIDE AND MOISTURE

PENETRATION

Stru

ctur

e C

ondi

tion

Concrete Deterioration

Parking Garage - Washington D.C.

Corrosion Assessment, Repair and Corrosion Mitigation

•6 level sub-grade parking facility

•2-bay split level design•Cast-in-place reinforced concrete

•Exposure to deicing chemicals causing concrete deterioration

Parking Garage

Elastomeric Coating performing poorly in areas of high traffic volume, i.e. ramps and areas near entrance

Current Condition

Soffit and Wall Damage

• Condition assessment• Corrosion potential

survey ASTM C876• Ground penetrating

radar ASTM D6432• Concrete material

samplingChloride concentration depth testing ASTM C1152

Scope of Work

Corrosion Potential Measurements

ASTM C876 - also known as half-cell potentialDetermines probability of active corrosion

Corrosion Potential Survey

• Electromagnetic evaluation of concrete• Reinforcement layout

• Location of embedded metals• Cover Depth• Qualitative condition of reinforced concrete

• Chlorides, moisture, and concrete deterioration attenuate GPR signal

Ground Penetrating Radar

GPR – Cover Depth Survey

Chloride Sampling

0

1000

2000

3000

4000

5000

6000

7000

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

Chlo

ride

Cont

ent (

ppm

)

Depth (in)

C1 C2 C3 D1 D2 Threshold Cover Depth - Average Cover Depth - +STDEV Cover Depth - -STDEV

•Severe corrosion damage on levels A, B and C• Delamination and spalling• Concrete with high chloride contact, active corrosion• Near entry way, exposed to most amount of traffic and deicing chemicals

•Little to no damage on level D, E and F• Deeper in the garage, less traffic and reduction in chloride exposure

•Corrosion activity on all ramps• Turning of vehicle wheels and more traffic lead to early deterioration of elastomeric coating, allowing greater chloride diffusion

Assessment

• Do nothing• Basic Repair

• Remove/replaced delaminated concrete

• Targeted Approach• CP to levels A,B, C and ramps• Imbedded galvanic anodes

• Global Approach• CP to all levels• ICCP – MMO titanium mesh

Rehabilitation Options

Anode Design Using Survey

Honolulu Club

GPR Survey

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Impact Echo

Pulse Velocity

Assessment of Concrete

Gethsemane Church

Corrosion Deterioration

Carbonation Corrosion

Corrosion Potential Survey

150 Bay Street

Reinforcement Layout

Chloride Sampling

Carbonation Depth

Venetian Isles

Pile Deterioration

Substructure Evaluation

Sacred Heart Hospital

•Strands don’t have the same level of protection

• Not encased in cement therefore the corrosion resistant film is not created

•Breaks in sheathing• Allow access for moisture and chlorides

•Poor greasing• Improperly caped anchors

• Access for moisture and chlorides

Unbonded PT

Exposed PT

PT Issues

Moisture Issues

Post-TechTM Corrosion Evaluation

0

10

20

30

40

50

60

70

80

90

100

10 12 14 16 18 20 22 24 26 28 30

Rel

ativ

e H

umid

ity (%

)

Temperature (oC)

Data CE M.C. 0.003K CE M.C. 0.007K

"Wet" Cables

"Wet/Dry" Cables

"Dry" Cable

Moisture Testing

Screwdriver Penetration Test

Grady CASS Parking Garage

Lateral Deflection Testing

Access the Tendons

Test No. Cycle Tendon Group Tendon

∆-2(final) ∆-1(initial) ∆2-∆1 Theoretical Corrected

(in) (in) (in) Tension (lb) Tension (lb)

11 197 B 0.510 0.275 0.235 22773 180102 197 B 0.503 0.287 0.216 24775 207843 197 B 0.408 0.193 0.215 24891 20943

AVG 0.474 0.252 0.222 24106 19856

21 191 A 0.460 0.222 0.238 22486 176122 191 A 0.468 0.248 0.220 24325 201603 191 A 0.470 0.246 0.224 23891 19558

AVG 0.466 0.239 0.227 23541 19073

31 190 A 0.377 0.175 0.202 26492 231622 190 A 0.370 0.174 0.196 27302 242853 190 A 0.367 0.175 0.192 27871 25073

AVG 0.371 0.175 0.197 27210 24157

41 185 C 0.604 0.304 0.300 17842 111772 185 C 0.591 0.328 0.263 20350 146523 185 C 0.61 0.346 0.264 20273 14545

AVG 0.602 0.326 0.276 19416 13357

Results

Kansas City Airport Hanger

• Tie-beam in floor of each hanger• 12 button head PT Tendons• 34 wires each tendon

Unbonded PT

• Observed wires sticking out of anchorage

Broken Wires

• Determine current stress tendons are under

Lift Off Testing

TendonMax Applied

Jack Pressure (psi)

Did Lift off Occur?

Tendon Load at Lift Off

(kips)

Effective Number of

Wires

Potential Number of

Broken Wires1 5050 Yes 243.0 34 12 5000 Yes 240.6 34 13 4850 Yes 233.4 33 24 4950 Yes 238.2 34 15 5150 Yes 247.8 35 06 5100 Yes 245.4 35 07 5000 Yes 240.6 34 18 5100 Yes 245.4 35 09 5000 Yes 240.6 34 1

10 4850 Yes 233.4 33 211 4050 Yes 194.9 28 712 5000 Yes 240.6 34 1

Lift Off Results

QUESTIONS?

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Contact Brian

Dr. Brian Pailes

Principal Engineer

VCS Inc.

Tampa, FL

Office: 813-501-0050

BrianP@VCServices.com

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