American University in Dubai A School of Engineering...
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American University in Dubai A School of Engineering Infrastructure Sustainability and Assessment Center Service Life Assessment of Concrete Structures in the GCC Countries By Mohamad Nagi
Transcript of American University in Dubai A School of Engineering...
American University in DubaiA School of Engineering
Infrastructure Sustainability and Assessment Center
Service Life Assessment of Concrete Structures in the GCC Countries
By
Mohamad Nagi
Corrosive Environment
What is DurabilityDurability by definition is the ability of concrete to resist weathering action, chemical attack, and abrasion while maintaining its desired engineering properties
Degradation Mechanisms
Chemical attack
• Leaching• Acid and base attack• Alkali-silica reactions• Delayed ettringite formation• Sulfate attack• Steel reinforcement corrosion
Physical attack
• Salt crystallization• Freezing-and-thawing attack• Abrasion, erosion, and
cavitation• Thermal damage
Degradation Mechanisms
Chemical attack
• Leaching• Acid and base attack• Alkali-silica reactions• Delayed ettringite formation• Sulfate attack• Steel reinforcement corrosion
Physical attack
• Salt crystallization• Freezing-and-thawing attack• Abrasion, erosion, and
cavitation• Thermal damage
Alkali Silica ReactivityThis is caused by reaction of certain aggregates with alkali in cement to form expansive gel that eventually leads to craking
Sulphate AttackA reaction between sulphate ions and calcium hydroxide and form gypsum and ettringite.
BRE and ACI 201 Classification in UAE
Low w/c ration and use of SCM
What is CorrosionWhat is Corrosion
Deterioration of a material as a result of reaction with its environment-M.G. Fontana
Destructive attack of a metal by chemical or electrochemical reaction with its environment-H.H. Uhling.
Metal corrode because they have a strong driving force to return to their natural state
Requirements for Corrosion
Cathode
Anode
Electrolyte
Electrical connection between anode and cathode
Definition of Anode&Cathode
Loss of electrons is oxidation
Gain of electrons is reduction
Chloride-Induced Corrosion of Steel in Concrete
Cathode and anode sites co-exist on the Steel
The steel is the conductor, and
Concrete acts as electrolyte
Passivity layer is damaged by chloride ions
-ClO2H2O
-ClO2H2O
United Corrosion Technologies ©2010
Why Should We Care About CorrosionWhy Should we Care about Corrosion
Safety
Conservation of Resources
Cost
Cost of Corrosion in the GCC States-2004Kingdom of Bahrain 0.5 B.
State of Kuwait 2.17 B.
Sultanate of Oman 1.3 B.
State of Qatar 1.1 B.
Kingdom of Saudi Arabia 13.0 B.
United Arab Emirates 3.7 B.
Environment
Depletion of iron ore resources
Concrete carbon foot-print
Service Life
One Century of Service Life
Is Required???
Codes are not written for our environment
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Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Avg Temp (Degrees C)
UAE
London
New York
Water SalinityRef. King Fahed University of Petroleum and Minerals
BlackSea
Med.Sea
NorthSea
AtlanticOcean
ArabianGulf
Red Sea
Cl- 9,500 21,270 16,550 20,000 36,900 22,660
SO3 1,362 2,596 2,220 2,180 5,120 3,050
Saline GroundwaterRef.CONCRETE SOCIETY – CS163 (Guide to the Design of Concrete Structures in the
Arabian Peninsula) table 5 - P. 15
SITE Cl- mg/Lin groundwater
SO4-2 mg/L
in groundwaterBurj Khalifa 17-90,000 2800-5900
Emirates Towers 66-81,000 1760-6330
Doha Convention Centre 31,000 4100(max)
Dubai Tower (Qatar) 6,400-30,000 1430-3600
Aweer 9,200 Not Measured
Service LifeService Life
The period of time during which a structure meets or exceeds the minimum requirements set for it
Requirements limitation can be technical, functional or economical
Durability
ASR Sulfate attack Corrosion
Kyosti Tuuti’s Service Life Model
Kyosti Tuuti’s Service Life Model
Time
Loss
of c
ross
-Sec
tion
Concrete CoverDiffusion Coefficient
Kyosti Tuuti’s Service Life Model
Time
Loss
of c
ross
-Sec
tion
Chloride ThresholdConcrete Cover
Diffusion Coefficient
Kyosti Tuuti’s Service Life Model
Time
Loss
of c
ross
-Sec
tion
Concrete CoverDiffusion Coefficient
Chloride Threshold
Corrosion Rate(µm/year)
End of Service Life
Kyosti Tuuti’s Service Life Model
Time
Loss
of c
ross
-Sec
tion
Concrete CoverDiffusion Coefficient
Chloride Threshold
Corrosion Rate(µm/year)
End of Service Life
How to Achieve it
Concrete Mix Design
Use of GGBS, Fly ash and Microsilica
Use of corrosion inhibitor and other corrosion preventive methods.
Construction practice Curing, surface protection, curing temperature
QA/QC procedures
Designing Durable Structures
ACI 318AASHTOEUROCODE 2BS 5400BS 8500CS 163
Guide to the Design of Concrete Structures in the Arabian Penn.Provides Exposure classes relevant
to the regionCategorizes structures as “Normal”
vs. “Special”
Special Structures
Service Life in excess of 30 yearsExposed to severe environmentRecommends Project-Specific Durability Study / Service-Life
PredictionAdditional Durability Enhancement Methods
Special Structures
Service Life in excess of 30 yearsExposed to severe environmentRecommends Project-Specific Durability Study / Service-Life
PredictionAdditional Durability Enhancement Methods
Structural Design
ACI 318 = ??? years AASHTO = 75 years EUROCODE 2 = 50 years BS 5400 = 50 years BS 8500 = 50 years
Additional Durability Enhancement Techniques
Admixtures Reinforcement Surface Electrochemical
WaterproofersCorrosion Inhibitors
Unreinforced DesignEpoxy Coated SteelCorrosion Resistant SteelGalvanized
Controlled Permeability FormworkSealersCoatings
MonitoringCathodic Protection
MEDRC ResearchSelected Concrete Mix Design.
Laboratory Tests
Service Life Prediction
Field Testing Stations
Standard Durability Tests
• Water Permeability, BS EN 12390/DIN 1048
• Water Absorption, BS 1881-122
• Rapid Chloride Penetration, ASTM C 1202
ASTM G 109 Test
ASTM G 109 Specimens
Further Research to Improve our Understanding of SLP
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Integrated
Current (C
oulombs)
OPC
OPC/MCI
ConclusionsThe Gulf region is considered the most corrosive location in the world
Corrosion is the main durability factor leads to deterioration of concrete structures
Use of Quality Concrete and good QA/QC system are the key to achieve the required service life
Use of corrosion protection systems such as corrosion inhibitors extend the service life of structures
Thank youشڪراً
Questions?
