bridge preservation: evaluation, repair and protection
TRANSCRIPT
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Bridge Preservation: Evaluation, Repair and ProtectionWebinar Wednesday Series
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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
vector-corrosion.com vcservices.com
ndtcorporation.com vector-construction.com
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WESAVESTRUCTURES.INFO• The construction industry is the
largest user of resources and raw materials.
• Approx. 40% of solid waste comes from construction and demolition.
• Making new structures last longer and the rehabilitation and reuse of existing structures saves money compared to the cost of premature failure, demolition and rebuilding.
• In addition to economic benefits, repairing and extending the service life of structures reduces the consumption of natural resources, pollution and construction waste.
https://www.wesavestructures.info/environmental-impact-calculator
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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 Vector Corrosion Services, 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 Concrete Bridge Elements
• Understanding the causeand effect of reinforcingsteel corrosion in concrete
• Quantifying the magnitudeand extent of corrosion risk.
• Many destructive and non-destructive test methods forassessing corrosion risk.
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What is Corrosion Reaction• Electrochemical Reaction
• Anode – where rust is formed
• Cathodic – no section loss
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Concrete Protects Steel
• Concrete is naturally alkaline• pH of about 13
• Steel is naturally passive at this alkalinity
• Formation of passive layer
• Passive layer can be destroyed by;• Chlorides• Carbonation
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Corrosion Induced Damage
• Damage resulting from
• Metal section loss and
• Formation of iron oxide (rust)
• Expansive properties of iron oxidecreate tensile stresses in concrete
• Leads to cracking, delamination,and eventual spalling
0 2 4 6 8Relative Size
Fe
FeO
Fe3O4
Fe(OH)2
Fe(OH)3*3H2O
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Corrosion Damage
Conventional Mild Reinforcing Bar
In most cases loss of steel section not primary concernTypically damage to concrete becomes significant and observable prior to severe section loss
High Strength Strands
Minor section loss of steel can have significant effect on strength
Steel can have significant section loss without significant concrete damage
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Concrete Preservation Process
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ACI 562: Concrete Repair Code
• Being adopted in states throughout the US
• Requires that an evaluation take place prior to designing repairs
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Delamination Survey
• Hammer sounding located areaswhere concrete has debonded
• Is there more going on here?
• Yellow – extent of delaminationthat cannot be heard throughhammer sounding
• Red – extent of activate corrosionthat will be a delamination in thenear future
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Why use NDT in Evaluation?
• We need to more accuratelydetermine location and extent ofdeterioration?
• Sounding and visual inspectionsare known to underestimate truerepair area
• Impacts of underestimating repairquantities?
• Costly change orders
• Increased project duration
• Time from inspection toconstruction can be long
• Deterioration will have grown fromlast inspection
NOT JUST FOR DECKS!
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Corrosion Deterioration and NDTREBAR 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
Rei
nfor
ced
Con
cret
e C
ondi
tion
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Visual Inspection
Identify areas of visual deterioration
• Rust Staining• Cracking• Spalling• Exposed Reinforcement• Water Seepage• Efflorescence
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Sounding Survey
• Hammer sounding or chain drag
• Locates areas of large nearsurface delaminations
• Incipient delaminations cannot beidentified
• False positives are rare
• False negatives are common
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Collection of Cores
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Chloride Sampling
• Chloride Threshold - Between 1 to 2 lbs of chloride per cubic yardof concrete
• 350 ppm of chloride in concrete is about 1.5 lbs per cubic yard
0
200
400
600
800
1000
1200
1400
1600
1800
0 0.5 1 1.5 2 2.5 3
Chl
orid
e C
once
ntra
tion
(ppm
)
Depth (in)
Chloride Concentration with Depth
Sample 1
Sample 2
Sample 3
Sample 4
Sample 5
Threshold
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Carbonation Depth
• Carbon dioxide permeates intoconcrete
• 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 – carbonationis a result of time and exposure
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Corrosion Potential Measurements
• ASTM C876
• Most people refer to it as the “half-cell” method
• Determines the probability ofactive corrosion of embeddedmetals
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Corrosion Potential – Bridge Deck
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Corrosion Potential – Substructure
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Ground Penetrating Radar
• 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
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GPR Locating Existing Reinforcement
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GPR Locating Existing Reinforcement
Manufactured
Void
Bituminous Overlay/Waterproof Membrane4.9 inches to 6.2 inches thick (roadway)
3.3-3 .6 inches overlay with 4-14 inches of fill (median)
6" 6"8"7"7"8"3" 3"
6"4"8"4"4"4"8"4"6"
5"4" 4" 4" 3" 4" 4" 3" 5" 4" 4" 4"
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Cover Depth Survey
• Cover depth is an important factorin the service life of a structure
• Reduced cover depths allow forchlorides and carbonation to reachsteel faster
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Chloride Diffusion
Concrete Carbonation
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GPR Cover Survey
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GPR Amplitude Survey
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Acoustic Methods – Impact Echo
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Acoustic Method – Pulse Velocity
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Relationship between Compressive Strength and Wave Velocity
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Acoustic Testing
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Acoustic Testing
1)
2)
3)
4)
Deck delaminations impact echo measurements at sensor #1
Longitudinal partial deck cracking measurements at sensor #2
Longitudinal full deck cracking measurements at sensor #3
Transverse deck cracking measurements at sensor #4
#1#2#3
#4
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Acoustic Deck Testing
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Acoustic Substructure Testing
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Delaminations Found by Sounding
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Delaminations Found by Impact Echo
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Acoustic In-Situ Compressive Strength
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Repair Area
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Infrared Thermography• Delaminations have different thermal properties than sound
concrete
• Result of air-gap caused from the separation of the concrete• In the morning sun, delaminations heat up faster than sound
concrete section
• During evening cooling, delaminations cool down faster thansound concrete section
• Allows for very quick assessment of large areas• Results are similar to chain drag and hammer sounding
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IR of Arch Bridge
• Hammer sounding surveydone several years prior
• Wanted to know growth ofdeterioration from lastsurvey
• IR provided a quick methodto resurvey the concrete
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Petrography
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QUESTIONS?
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Contact Dr. Pailes
Dr. Brian PailesPrincipal EngineerVector Corrosion ServicesTampa, FL
Office: 813-501-0050 [email protected]
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PROFESSIONAL DEVELOPMENT HOURS
• PDH certificates available
• Complete webinar evaluation
• Evaluation form link available:• In webinar chat• Via E-mail• QR code here
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WEBINAR RECORDING & FUTURE EVENTS
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CONCRETE PRESERVATION ALLIANCE
WESAVESTRUCTURES.INFO