corrosion assessments for parking structures
TRANSCRIPT
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.
WeSaveStructures.info
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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
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