Modeling of Chloride Penetration into Concrete under Airborne Chloride Environmental Conditions Combined with Washout Effects

Abstract

In marine environments, deterioration of concrete infrastructures under airborne chloride attack is a common problem, which raises the need for a reliable prediction model of airborne chloride penetration into concrete structures to evaluate the service life of concrete structures. This study proposes a time-dependent computational model for predicting the amount of airborne chloride ingress into concrete under actual environmental conditions. The proposed model calculates the amount of chloride penetration by considering the amount of advection and diffusion of airborne chloride on the concrete surface. To compute the amount of airborne chloride penetration, the proportion of dry and wet sections on the concrete surface is assumed, and to ensure accurate prediction of chloride penetration into concrete structures under actual environment conditions, the washout effect of rainfall is taken into account in the calculation. The proposed model was verified through comparison of the experimental and on-site measurement results.

Comprehensive Numerical System for Predicting Airborne Chloride Generation and Its Ingress in Concrete under Actual Environmental Conditions

“…However, to predict the amount of airborne chloride penetration, the original DuCOM system cannot be used directly due to the different boundary conditions during airborne chloride exposure conditions. When a structure is exposed to airborne chloride, only some parts of the structure are wet and other parts remain dry (Wattanapornprom and Ishida 2017). Thus, chloride and water ingress do not occur uniformly on the concrete surface.…”

“…In moisture transport, both vapor and liquid phases of mass transport are considered. The moisture distribution and (Maekawa et al 1999(Maekawa et al , 2008Ishida et.al 2007;Iqbal and Ishida 2009;Takahashi and Ishida 2016;Wattanapornprom and Ishida 2017). However, to predict the amount of airborne chloride penetration, the original DuCOM system cannot be used directly due to the different boundary conditions during airborne chloride exposure conditions.…”

“…However, in the actual environmental conditions, C o depends on the amount of airborne chloride, which varies depending on wind direction, wind speed, wave height, obstacles such as wave breakers and cliffs, distance from the seashore, and so on (Bongochgetsakul et al 2011). Moreover, C o is also affected by rainfall and melted snow as water can wash out chloride from the concrete surface (Yamashita et al 2007;Wattanapornprom and Ishida 2017). Further, observational data from the Public Works Research Institute -PWRI (1993) show that the concentration of chloride on the concrete surface also depends on the concrete mix proportions.…”

“…Recently, a modeling of chloride ingress in concrete structure under airborne chloride environments has been developed (Wattanapornprom and Ishida 2017). This model can determine the amount of chloride penetration under actual environmental condition.…”

“…In the second step, the airborne chloride ingress model developed by the authors (Wattanapornprom and Ishida 2017) calculates the amount of chloride penetration by considering the amount of advection and diffusion of airborne chloride on the concrete surface. The amount of chloride penetration into concrete depends on concrete mix proportions, curing conditions, relative humidity (RH), rainfall intensity, and various other factors (Wattanapornprom and Ishida 2017). Hence, the amount of airborne chloride from the first step and the environmental conditions and concrete mix proportions are used as an input for the airborne chloride ingress calculation.…”