• Journal of the Korea Concrete Institute
• /
• v.24 no.4
• /
• pp.481-490
• /
• 2012

Evaluation of chloride penetration is very important, because induced chloride ion causes corrosion in embedded steel. Diffusion coefficient obtained from rapid chloride penetration test is currently used, however this method cannot provide a correct prediction of chloride content since it shows only ion migration velocity in electrical field. Apparent diffusion coefficient of chloride ion based on simple Fick's Law can provide a total chloride penetration magnitude to engineers. This study proposes an analysis technique to predict chloride penetration using apparent diffusion coefficient of chloride ion from neural network (NN) algorithm and time-dependent diffusion phenomena. For this work, thirty mix proportions with the related diffusion coefficients are studied. The components of mix proportions such as w/b ratio, unit content of cement, slag, fly ash, silica fume, and fine/coarse aggregate are selected as neurons, then learning for apparent diffusion coefficient is trained. Considering time-dependent diffusion coefficient based on Fick's Law, the technique for chloride penetration analysis is proposed. The applicability of the technique is verified through test results from short, long term submerged test, and field investigations. The proposed technique can be improved through NN learning-training based on the acquisition of various mix proportions and the related diffusion coefficients of chloride ion.

• Journal of the Korean Ceramic Society
• /
• v.36 no.3
• /
• pp.260-265
• /
• 1999

보통 포틀랜드 시멘트와 플라이애쉬, 슬래그를 혼합한 혼합시멘트 경화체를 이용하여 이온 확산에 미치는 혼합재의 영향과 양이온 공존시 염소이온의 확산에 대하여 고찰하였다. 겉보기 이온확산계수가 보통 포틀랜드의 시멘트보다 플라이애쉬와 슬래그를 혼합한 시멘트 경화체가 약 10-3배로 매우 낮은 값을 나타내었다. 이것은 포졸란 반응에 의해 많은 CSH 수화물이 capillary pore에 형성되어 macro pore가 감소되고 micro pore가 증가되어 이온 확산에 대한 저항이 커졌기 때문이다. 또한, Mg2+이온 공존시에 염소이온의 확산은 증가되었다.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.23 no.6
• /
• pp.18-25
• /
• 2019

The cracks occurred during service life of concrete structure should be considered in durability design, because of the concrete's material property which is weak in tensile strength. In this study, the fly ash concrete mixtures considering 2 levels of strength is designed and outdoor exposure tests are conducted for those concrete specimens. The exposure environment is set to a splash zone, and in order to evaluate the effect of crack width on the behavior of chloride diffusion, the crack width of up to 1.0 mm is generated at intervals of 0.1 mm at each concrete mixture. After that, apparent chloride diffusion coefficient and surface chloride contents are deducted considering 3 levels of exposure periods(180 days, 365 days, 730 days). The diffusion coefficients of two types of mixture increase with the increase of crack width, and the diffusion coefficients decrease with the increase of exposure periods. In addition, the effect of the crack width on the diffusion coefficient is reduced as the exposure periods increase, which is attributed to the extra hydrate by chloride ion reducing the diffusivity of concrete. The behavior of the surface chloride contents does not significantly change by the increase in crack width, compared to the behavior of apparent chloride diffusion coefficient. Also, In the high strength FA concrete mixture, the surface chloride contents are 78.9 % ~ 90.7 % than the normal FA strength concrete mixture. Thus, Surface chloride contents have correlation with the strength of concrete.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2003.11a
• /
• pp.541-544
• /
• 2003

Chloride diffusivity is one of the important properties of concrete affecting the durability of a structure. The diffusivity for porous materials is determined conventionally by immersion in a solution. However, this method is complicate and time-consuming, often requiring months or years to obtain results. Thus, the application of colorimetric method to estimate the apparent diffusivity of chloride ion was verified in this study. The result reveals that the apparent diffusivity of chloride ion can be predicted to use colorimetric method. Additionally the colorimetric method is capable to predict the profile of chloride ion.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.23 no.3
• /
• pp.119-126
• /
• 2019

In case of RC(Reinforced Concrete) structures which are constructed in coastal areas, chloride ions in sea water corrode the steel rebar in concrete. Especially in coastal areas, RC structures are affected by not only immersion of sea water, but also tidal of sea water and airborne chloride ions. In this study, marine environment exposure tests are conducted, considering 3 types of exposure environments(immersion zone, tidal zone, splash zone) and the exposure periods of 180 days, 365 days, and 730 days. Also, the concrete mixtures for this study are established, considering 3 levels of W/B(Water to Binder) ratio(0.37, 0.42, 0.47) and 2 levels of substitution rate of Fly ash(0 %, 30 %). In all exposure environments, Fly ash concrete has lower apparent chloride diffusion coefficients than OPC concrete. It is thought that fly ash's pozzolan reaction improves chloride resistance of concrete. Fly ash concrete has up to 63.5 % of decreasing rate in 180 days of exposure and up to 55.8 % of decreasing rate in 730 days of exposure, based on diffusion coefficients of OPC concrete. As a result of evaluation about effects of exposure environments, apparent chloride diffusion coefficients of fly ash concrete are evaluated in order of tidal zone, immersion zone, and splash zone. In tidal zone, It is thought that repeated cycles of wetting and drying of sea water cause the diffusion of chloride ions rapidly.