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Measuring, Modelling and Monitoring Chloride ingress and Corrosion initiation in Cracked Concrete (M3C4)
Measuring, Modeling and Monitoring Chloride ingress and Corrosion initiation in Cracked Concrete (M3C4)
PhD students: Branko Šavija, José PachecoSupervisors: Prof. Erik Schlangen, Prof. Rob B. Polder
PERSPECTIEF Program IS2C “Integral Solutions for Sustainable Construction”
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Measuring, Modelling and Monitoring Chloride ingress and Corrosion initiation in Cracked Concrete (M3C4)
Durability
Stringent requirements!New contract types! (DBOM - design+build+operate+maintain)
Deterioration• Freeze-thaw damage• Sulphate attack• Alkali-aggregate reaction• Carbonation• Chloride induced corrosion
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Measuring, Modelling and Monitoring Chloride ingress and Corrosion initiation in Cracked Concrete (M3C4)
Cracking
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Measuring, Modelling and Monitoring Chloride ingress and Corrosion initiation in Cracked Concrete (M3C4)
Why study chloride ingress and reinforcement corrosion in cracked concrete?
• Cracking- inevitable in concrete structures.• Cracks- fast route for ingress of deleterious species. • Might seriously reduce the service life!• Not properly taken into account by current service life models!• Long term effects are unknown!
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Measuring, Modelling and Monitoring Chloride ingress and Corrosion initiation in Cracked Concrete (M3C4)
Codes of practice prescribe (for aggressive environmental conditions):• Maximum surface crack width.• Minimum concrete cover depth (depending on the concrete quality).
• Simple models provided by the codes (e.g. Eurocode) for crack calculation suggest that larger covers give larger surface crack widths, which discourages designers from using them for durability design!
Contradictory?
Code Maximum crack width (mm)
ACI-222 (2002) 0.15
CEB/FIB Model Code (1990) 0.30
BS 8110 (1997) 0.30
ENV 1991-1-1 (1992) 0.30
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Measuring, Modelling and Monitoring Chloride ingress and Corrosion initiation in Cracked Concrete (M3C4)
200μm
360μm
600μm
250μm
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Measuring, Modelling and Monitoring Chloride ingress and Corrosion initiation in Cracked Concrete (M3C4)
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Measuring, Modelling and Monitoring Chloride ingress and Corrosion initiation in Cracked Concrete (M3C4)
Numerical simulations:
Coarse aggreg
ate
MortarInterfa
ce
2
2
C CD
t x
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Measuring, Modelling and Monitoring Chloride ingress and Corrosion initiation in Cracked Concrete (M3C4)
Heterogeneous vs. homogeneous (sound) concrete:
D(×10-12
m2/s)
Concrete 47.614
Mortar 48.35
Interface 145.06
Aggregate ~0
Experiments by Yang & Wang (2004)
90 day chloride ponding
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Measuring, Modelling and Monitoring Chloride ingress and Corrosion initiation in Cracked Concrete (M3C4)
Sound vs. cracked concrete (mortar):
Numerically verified using experimental results of Ismail et al (2008)
Simulation results validated on results by Sahmaran (2007)
Surface crack width 369μm
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Measuring, Modelling and Monitoring Chloride ingress and Corrosion initiation in Cracked Concrete (M3C4)
Rapid chloride migration (RCM)
• Chloride ingress accelerated by applying voltage across the specimen
• Initially proposed by Tang and Nilsson (1993)
• Standardized in NT Build 492• Widely used in practice and research due
to its brevity and simplicity• Widespread use also in the Netherlands
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Measuring, Modelling and Monitoring Chloride ingress and Corrosion initiation in Cracked Concrete (M3C4)
Rapid chloride migration (RCM)
Heterogeneous concrete (mortar+gravel+interface)
4, 8, 12, 16, and 20 h of exposure
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Measuring, Modelling and Monitoring Chloride ingress and Corrosion initiation in Cracked Concrete (M3C4)
Self-healing of cracks:Self-closing is the expression for the fact that the width of a through-
crack diminishes with time. Causes are manifold:1) Physical2) Chemical3) Mechanical
Could influence chloride penetration, but depends on the environment, crack width, and possibly concrete composition.
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Measuring, Modelling and Monitoring Chloride ingress and Corrosion initiation in Cracked Concrete (M3C4)
Other ongoing work
• Monitoring corrosion behaviour of cracked specimens
• Development/use of advanced chloride mapping techniques (EDS, LIBS)
• Participation in RILEM TC-235 (CTC) Round Robin Test
• Influence of cracking on corrosion process• Characterization of the corrosion products (XRD)• Modelling cover cracking due to reinforcement
corrosion (mechanical model)
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Measuring, Modelling and Monitoring Chloride ingress and Corrosion initiation in Cracked Concrete (M3C4)
• See our latest results at:http://microlab-m3c4.blogspot.com/
Branko Š[email protected] Microlab, CiTG, 6.05+31152788986
José [email protected]+31152788990
