1. Chloride-induced-corrosion of steel bars embedded in concrete: A review
Dr. Anwar Khitab
Department of Civil Engineering
MIRPUR UNIVERSITY OF SCIENCE AND TECHNOLOGY
MIRPUR, AZAD KASHMIR

2. How chloride ions penetrate through concrete
Cl-
Saline Water
Concrete
Reinforcement
X (distance from concrete surface)
Chloride concentration
Chloride Profile
Time

3. Impact on Structures

4. Chloride profiles in reinforced concrete

5. Prediction of corrosion with chloride penetration into concrete

6. Modelling of chloride diffusion through cementitious materials
The typical approach to characterize diffusive transport of ions in porous materials begins with Fick’s law of diffusion.
Whenever a concentration gradient of a species c/x exists in a substance, the species will have the natural tendency to move in order to distribute itself more evenly within the substance and decrease the gradient.
The mathematics of this transport mechanism was formalized in 1855 by Adolf Fick, who, while working with salts postulated that the flux of material across a given plane is proportional to the concentration gradient across that plane.

7. Drawbacks of Fick’s Law
Penetration of chlorides: One of the major causes of corrosion of steel bars in concrete
Classical Approach: Fick’s Laws (For molecules)
Correct Approach: Equation of Nernst-Planck (For ions)
Fick’s 2nd law
Nernst-Planck Di

8. Mathematical Solution of Fick’s second Law
                                                                   (x14)
                                                                  gaussian.xls - gausslin.gif
Mathematical Solution of Fick’s second Law
x = Distance from the surface
Cs = Environmental surface concentration of chlorides
Erfc = Error function
D = Chloride diffusion coefficient in concrete, a measure of chloride speed in concrete
t = Duration of exposure to chloride

9. Nernst Planck Equation
Different Models
Fick’s Law
Nernst Planck Equation
Error Function Law
False Error Function Law
Duracrete
ClinConc
SELMER
Hetek
JSCE
Life-365
LEO
LERM
Li and Page
STADIUM
Johannesson
STANISH
MsDiff

10. What common input parameters are needed to run the model
Chloride diffusion coefficient
Initial chloride concentration within concrete
Environment chloride concentration

11. How chloride diffusion coefficient is determined?
By immersion tests (Minimum 35 days)
By Diffusion cell methods (extends over years)
By electrochemical methods (Maximum one week)

12. Immersion Tests
NaCl solution
Concrete specimen
Cl-

13. Diffusion and Electrochemical Tests
Solution containing chlorides
Same Solution without chlorides
Concrete specimen
Solution containing chlorides
Same Solution without chlorides
Concrete specimen

14. Modelling and Simulations with Erfc model

15. Modelling with MsDiff

16. Conclusions
The chloride ingress models, based on Fick’s laws of diffusion are quite simple but unfortunately not correct.
The models based on Nernst Planck equation are although sofiticated and correct but a lot of input parameters.
In Fick’s laws models, total chloride profiles are only calculated, which again is not a correct approach because in reality, these are free chlorides present only in the pore solution, which are resposible for the initiation of corrosion.

17. Publications on the topic by the Author
Ionic transport through saturated and reactive porous media, NATO Advanced Study Institute: Emerging Technologies in Porous Media, June 9-20, 2003.
Chloride diffusion through saturated concrete: numerical and experimental results, Advances in Concrete through Science and Engineering, Evanston (Illinois, USA), March 21-26, 2004.
Ionic contamination and decontamination of porous media, NATO Science Series for Peace: Physics, Chemistry, Mathematics, pp , Springer, Netherlands, 2004.
Predictive model for chloride penetration through concrete, Magazine of Concrete Research Vol:57 pp: , 2005.
Chloride attack through concrete: time effects, (2006) ACI Special Publications Vol:234 pp:
Modeling of Chloride Penetration through concrete, First Abasyn International Conference on Management and Technology (ABICMT-2013), May 2013, Peshawar.
Modeling of Chloride Diffusion through Concrete using Fick’s laws of Diffusion, 2nd Annual Computational Science Conference, October 20-25, 2013, International Islamic University, Islamabad.
Modeling Of Chloride Ingress In Concrete Using Fick's Laws: Review And Historical Perspective, Sci.Int. 26(4), , 2014 ISSN