Influence of chemical spray sealing on the durability of HSC

Problem statement

It is well known that chloride is a cause of reinforcement corrosion in concrete structures. Generally speaking, capillary pores are a path for chloride penetration in sound concrete. However, cracks can be a main path for chloride penetration in cracked concrete, as shown in Figure 1. Thus, the penetration of chloride into concrete through the cracks can have a significant harmful effect on the durability of concrete.

Figure 1: Chloride penetration through crack in concrete

Research objective

The primary purpose of this project is to examine the effect of cracks on chloride penetration. This work package consists of two sub-objectives; first, to define the mechanism of chloride penetration through cracks, and second, to formulate a model to predict chloride penetration. The model should be expressed as a function of relative penetration coefficient in cracked and sound concrete. The model will be set up in such a way that it is part of a general framework for predicting chloride profiles of cracked concrete.

Achievements so far

In order to examine the effect of cracks in terms of chloride penetration, concrete specimens with various crack width / crack length have been subjected to rapid chloride migration experiments. A theoretical approach to get a chloride diffusivity of only cracked zone excluding sound zone is established to quantify a value of critical crack width which can impact on chloride penetration. The initial results of this work indicate a critical crack width of 0.03 mm. Cracks smaller than this critical crack width are considered not to have a significant influence on the rate of chloride transport inwards, while chloride penetration does proceed faster above this critical crack width.
In the meantime, a phenomenological model to describe simply the characteristics of chloride penetration though cracks is suggested. In this model, cracked concrete is divided into three zones. Going from the surface inwards there is a penetration free zone, a penetration hardening zone and a pure diffusion zone. The criteria to divide three zone like this is based on the mechanism of penetration. The behavior of chloride penetration in the first and the third zone may be governed by Hagen-Poiseuille law and Fick’s diffusion law, respectively. In the penetration hardening zone, the second zone, the penetration may be governed by both of these two laws. This penetration behavior is expected as a turbulent flow because micro-cracks are not connected to each other in this portion. Henceforth, the experiment will be concentrated to define the penetration behavior of this zone..

Publications

I.S. Yoon, “New Approach of Chloride Binding Isotherm of Concrete,” Conference of Korea Concrete Institute, November, 2006

I.S. Yoon, E. Schlangen, K. van Breugel, “The Investigation of Crack Widths for the Effect of Cracks on Chloride Penetration of Concrete,” Journal of Korea Concrete Institute, Vol.18, No.2, November, 2006

I.S. Yoon, “Theoretical Approach to Calculate Surface Chloride Content of Submerged Concrete Exposed to Marine Environment,” Conference of Korea Concrete Institute, November, 2006

I.S. Yoon, “The Effect of Cracks on Chloride Penetration in Concrete: Phenomenological Model,” Journal of Korea Concrete Institute, Vol.19, No.1, Feb., 2007

I.S. Yoon, “Theoretical Modeling of Critical Chloride Content for (Non)Carbonated Concrete,” Conference of Korea Concrete Institute, May, 2007

I.S. Yoon, “Multi-Factor Function of Chloride Diffusivity of (Non)Carbonated Concrete” Conference of Korea Concrete Institute, May, 2007

I.S. Yoon, E. Schlangen, K. van Breugel, “The Effect of Increasing CO2 Concentration on Carbonation of Concrete Structures,” 3rd International Symposium – Sustainability in Cement and Concrete, Istanbul, Turkey, May, 2007

I.S. Yoon, “In-Situ Investigation of Durability Performance of RC Bridges in Metropolitan,” 3rd International Symposium – Sustainability in Cement and Concrete, Istanbul, Turkey, May, 2007

I. S. Yoon, E. Schlangen, M. R. de Rooij, K. van Breugel, “The Effect of Cracks on Chloride Penetration into Concrete,” 6th International Conference on Fracture and Damage Mechanics, Madeira, Portugal, July, 2007

I.S. Yoon, “Estimation of Required Cover Depth for Concrete Bridge Decks Due to De-icing Salts Based on In-Situ Investigation,” SEMC07, Cape Town, South Africa, Sept., 2007, accepted

I.S. Yoon, “The Effect of Carbonation on Material Parameters of Chloride Penetration Model in Concrete,” Journal of Korean Society of Civil Engineering, 2007, accepted

I.S. Yoon, “Analytical Formulation of Critical Chloride Content for (Non)Carbonated Concrete Considering Characteristics of Cement Hydration,  Journal of Korea Concrete Institute, 2007,  accepted

I.S. Yoon, “Modelling of Materials Parameters of Marine Concrete for Service Life Prediction,” Journal of Key Engineering Materials, Trans Tech Publication, July, 2007, accepted

I.S. Yoon, “Experimental Study on Combined Deterioration of Concrete Due to Carbonation and Chloride Penetration,” Journal of Key Engineering Materials, Trans Tech Publication, July, 2007, accepted

I.S. Yoon, “New Approach of Critical Chloride Content in (Non)Carbonated Concrete,” Journal of Key Engineering Materials, Trans Tech Publication July, 2007, accepted

I.S. Yoon, “The Effect of Cracks on Chloride Penetration into Concrete,” Journal of Key Engineering Materials, Trans Tech Publication July, 2007, accepted

I.S. Yoon, “The Effect of Increasing CO2 Concentration on Carbonation of Concrete Structures,” Journal of Atmospheric Environment, 2007, accepted

I.S. Yoon, “Theoretical Time Evolution of Critical Chloride Content in Concrete,” ACI Material Journal, 2007, submitted for publication

I.S. Yoon, M. R. de Rooij, E. Schlangen, and K.van Breugel, “Critical Crack Width to Consider Influence on Penetration of Chlorides into Concrete,” ACF conference, submitted for publication.

I.S. Yoon, “Simulation of Critical Chloride Content in Pore Solution of Concrete,” HERON, submitted for publication.

I.S. Yoon, “Phenomenological Model and Critical Crack Width to Consider Influence of Micro-cracks on Chloride Ions Penetration of Concrete in Terms of Diffusion”, Journal Korea Concrete Institute, submitted for publication.

I.S. Yoon, “The  Effect of Cracks on Chloride Penetration in Concrete II: Examination of Critical Crack Width,” Journal of Korea Concrete Institute, 2007, submitted for publication.

I.S. Yoon, “Thermodynamic Formation of Chloride Binding Isotherm of Concrete,” Journal of Korea Concrete Institute, 2007, submitted for publication.

I.S. Yoon, “The Effect of Crack Width and Depth on Chloride Penetration into Concrete,” ACI Material Journal, 2007, finishing a draft.