Probabilistic Model for Assessing Chloride Threshold for Variable bar Lengths in Reinforcement Corrosion
Keywords:
Acceptable threshold value, characteristic length of rebar, acceptability coefficientAbstract
The focus of this study is on assessment of acceptable thresholds for chlorides (or failure probability) appropriate to the length of exposed structural member, from recommended threshold. It is commonly known that chlorides in exposed concrete induce corrosion (or pitting) in rebar. However, to initiate the corrosion process at the rebar surface, the content of chlorides has to exceed a certain threshold value. A plethora of environmental factors (micro and macro-climatic) can trigger the initiation of chlorideinduced corrosion in rebar that a single, globally accepted threshold value for chlorides with general applicability, does not exist. Nevertheless, research has recommended several thresholds for the onset of corrosion in different exposure environment. The acceptable threshold for chlorides can be described from the recommended via a statistical transform, by treating it as a size-dependent statistical phenomenon, for which theory of probabilistic reliability applies. This is because corroding spots on any surface of steel reinforcement and carbonated concrete are randomly distributed and appear to depend on the size of member. Therefore, it is suggested that the acceptable threshold for corrosion initiation, in reinforcing bar lying within carbonated concrete, be assessed statistically against a measurable structural length rather than service environment.
References
Angst, U. (2011). Chloride induced reinforcement corrosion in concrete, Concept of critical chloride content – methods and mechanisms. Thesis for the degree of Philosophiae Doctor, Trondheim.
Ballim Y., Alexander M. G. and Beushausen H. (2009). Durability of concrete. In: G. Owens, (ed.) Fulton’s concrete technology (9th ed.) Midrand: Cement and Concrete institute, pp. 155-188.
Bertolini, L. (2008). Steel corrosion and service live of reinforced concrete structures. Structure and infrastructure Engineering, 4(2), 123-137.
Breit, W. (1997a). Kritischer korrosionsauslösender Chloridgehalt – Teil 2: Untersuchungen a Stahl in chloridhaltigen alkalischen Lösungen’, KurzberichtNr. 69, ibac, RWTH Aachen.
Broomfield, P. (2007). Corrosion of Steel in Concrete: Understanding, Investigation and Repair Book.
DuraCrete (1998). Modeling of deterioration, BRITE EURAM. In: Alisa, M., Andrade C., Gehlen C., Rodriguez J. and Vogels R. (Eds) Probabilistic Performance based Durability Design of Concrete Structures, project document No. BE95-1347/R4- 5pp. 174.
EN 1990-EC 1- Basis of structural design, CEN, Brussels, 2002.
EN 1992-EC 2: Design of Concrete Structures, CEN, Brussels, 2004
Foliæ, R. (2009). Durability and service life of concrete Structures-Design modeling, PAM, Bulletin for Applied and Comp. Math. (BAM), Budapest, Nr. 2195, pp. 33- 44.
Glass, G. K and Buenfeld, N. R. (1995). Chloride threshold levels for corrosion induced deterioration of steel in concrete. In: L. O. Nilsson and J. Ollivier (Eds.) Chloride penetration into concrete (pp. 398-406).
Glass G. K., Hassanein N. M. and Buenfeld N. R. (1997, December). Neural network modeling of chloride binding. Magazine of Concrete Research, 49(181), 323–335.
Hope, B. B. and Alan, I. K. (1987). Chloride corrosion threshold in concrete. ACI Material Journal, 84, 306-3014.
Kraker A., de Tichler J. W. and Vrouwender A. C. W. M. (1982). Safety, Reliability and Service Life of Structures. Heron, 27 (1), Delft. p. 85
Polder, R. B. (2009). Critical chloride content for reinforced concrete and its relationship to concrete resistivity. Journal of material and concrete, 60 (8), 623- 630.
Schiessl, P. and Lay, S. (2005). Influence of concrete composition. Wood head Publishing Ltd and CRC Press LLC © 2005, Wood head Publishing Ltd, TU München, Germany.
Schiessl P., Gehlen C. and Pabsch G. (2004). Prediction of service Life of existing Structures by Applying Probabilistic Service Life Design (SLD) Procedures, International Conference Advances in Concrete and Structures (ICACS 2003), Jiangsu, China.
Siemes, A. J. M. and Rostam, S. (1990). Durable Safety and Serviceability - A Performance Based Design Format, IABSE Report 74: Proceedings IABSE Colloquium “Basis of Design and Actions on Structures - Background and Application of Eurocode 1, Delft, pp. 41-50.
Siemes A., Wrouwenvelder A. and Beukel A. (1985). Durability of Buildings-A Reliability Analysis. Herron, 30(3), Delft. 3-48.
Sobhani, J. and Ramezaninpour, A. A. (2010). A sensitivity analysis on chlorideinduced corrosion initiation time of RC. Elements. The 3rd International Conference on Concrete and Development/955. CD06-010.
Tuutti, K. (1980). Service life of structures with regard to embedded steel. ACI Special publication, 65.
Tuutti, K. (1982). Corrosion of steel in concrete. Swedish Cement and Concrete Research Institute.
