• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.5
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• pp.66-74
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• 2016

The objective of this study is the investigation of the influence of carbonation on the penetration of chloride ions in reinforced concrete sections for different mix proportions and environmental conditions. A comprehensive numerical model based on the change of the pore structure and the chemical equilibrium was used for this combined action of carbonation and chloride ingress. The empirical formulae of some parameters in this model are estimated according to numerous experimental data. And, a set of data analysis is carried out to simplify the estimation of model variables to reduce the computational cost. A coupled simulation of the transports of carbon dioxide, chloride ions, heat and moisture is carried out. Then, the parametric analysis is given and the numerical results show that the effect of carbonation of the free chloride ingress is significant and depends on the binder types and concrete mix proportion.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10a
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• pp.429-432
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• 2000

The studies on chloride diffusion of concrete have been done so far by many researchers. However, there are few studies on the effects of other attacks, like carbonation, on chloride diffusion properties. In this study, the experiments are carried out focusing on this by varying cement type, water to cement ratio and replacement of fly ash of concrete. The results show that carbonation attacks do not affect greatly chloride diffusion properties of plain concrete, while the different tendencies are exhibited for fly ash concrete. Therefore, it is desirable to consider the effects of carbonation attacks on the chloride diffusion model to predict accurately the penetration of chloride ion fly ash is partially replaced for cement.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2012.05a
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• pp.215-216
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• 2012

Emissions of CO₂ occur during the production of cement manufacturing process. During the production of clinker, limestone is mainly calcium carbonate, is heated to produce lime and CO₂ as a by-product. It has a major problem, CO₂ uptake is not considered in concrete carbonation, just focus in CO₂ emission. This study is to develop a simulation model for CO₂ uptakes in concrete structures based on carbonation reduction coefficient considering finishing materials. CO₂ uptakes unit of concrete cubic meter is calculated by CO₂ emissions unit of concrete materials and usage of concrete materials in mix proportion. From the simulation result, CO₂ uptake ratios is 2.04 percent in carbonation models of concrete structure during 40 years.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.5
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• pp.119-127
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• 2010

This paper provides a new approach for durability prediction of reinforced concrete structures exposed to carbonation. In this method, the prediction can be updated successively by a Bayes' theorem when additional data are available. The stochastic properties of model parameters are explicitly taken into account in the model. To simplify the procedure of the model, the probability of the durability limit is determined based on the samples obtained from the Latin Hypercube Sampling(LHS) technique. The new method may be very useful in design of important concrete structures and help to predict the remaining service life of existing concrete structures which have been monitored. For using the new method, in which the prior distribution is developed to represent the uncertainties of the carbonation velocity using data of concrete structures(3700 specimens) in Korea and the likelihood function is used to monitor in-situ data. The posterior distribution is obtained by combining a prior distribution and a likelihood function. Efficiency of the LHS technique for simulation was confirmed through a comparison between the LHS and the Monte Calro Simulation(MCS) technique.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.233-236
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• 2006

Chloride attack and carbonation induced corrosion of reinforcement are those of the main factors which cause the deterioration of concrete structures. The objective of this study is to suggest an analytic model for the prediction of chloride penetration into carbonated concrete, in order to make up for the current codes. Carbonation depth model considering the moisture effect is validated by being compared with the test data and the analytic model on chloride penetration into carbonated concrete is developed. Finally, the corrosion-initiation time has been predicted by the present model, being compared with that by the current code equation. The comparison shows that the current code equation can underestimate the chloride penetration into carbonated concrete in marine atmospheric conditions.

• Proceedings of the Korean Nuclear Society Conference
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• 2001.05a
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• pp.484.1-484
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• 2001

• International Journal of Concrete Structures and Materials
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• v.6 no.3
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• pp.155-163
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• 2012

In order to predict the neutralization of concrete which is the reaction of carbonation dioxide from the outside and cement hydration product, such as calcium hydroxide and C-S-H, it was studied the numerical analysis method considering change of the pore structure and relative humidity during the neutralization reaction. Diffusion-reaction neutralization model was developed to predict the neutralization depth of concrete with coating finishing material. In order to build numerical analysis models considering outdoor environment and finishing materials, the adaption of proposed model was shown the results of existing outdoor exposure test results and accelerated carbonation test.

• Journal of the Korea Concrete Institute
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• v.21 no.3
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• pp.255-264
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• 2009

Permeability coefficient of concrete is a substaintial key parameter for understanding the durability performance of concrete and its microstructural densification. Many researches for the issue have been accomplished, however, it is very rare to deal with the theoretical study on permeability coefficient in connection with carbonation of concrete and the the effect of volumetric fraction of cement paste or aggregate on the permeability coefficient. The majority of these researches have not dealt with this issue combined with carbonation of concrete, although carbonation can significantly impact on the permeability coefficient of concrete. The purpose of this study is to establish a fundamental approach to compute the permeability coefficeint of (non)carbonated concrete. When simulating a microstructural characteristics as a starting point for deriving a model for the permeability coefficient by the numerical simulation program for cementitious materials, HYMOSTRUC, a more realistic formulation can be achieved. For several compositions of cement pastes, the permeability coefficient was calculated with the analytical formulation, followed by a microstructure-based model. Emphasis was on the microstructural changes and its effective change of the permeability coefficient of carbonated concrete. For carbonated concrete, reduced porosity was calculated and this was used for calculating the permeability coefficeint. The computational result was compared with experimental outcome.

• Journal of the Korea Concrete Institute
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• v.15 no.4
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• pp.574-584
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• 2003

The most common deterioration cause of concrete structures in urban environment is carbonation. Recently, the $CO_2$ concentration and temperature at atmosphere is sharply increased with time due to global warming phenomena. In this study, the climate scenario IS92a, which was suggested by the IPCC, is used to consider temperature and atmospheric $CO_2$ concentration change in the model of service life prediction. The modified mathematical solution, which was based on the Fick's 1st law of diffusion, was used to reflect concrete materials properties such as the degree of hydration of concrete with elapsed time, and important parameters, which associated with deterioration rate. The techniques of service life prediction are developed introducing the method of reliability and stochastic concept to consider microclimatic condition in Seoul, South Korea. From the result of service life prediction, concrete containing high W/C ratio is shown fast carbonation rate due to $CO_2$ concentration increase. It is concluded that the deterioration of concrete structures due to carbonation is insignificant problem on the conditions that below W/C 55%, well curing concrete.

• Journal of the Korea Concrete Institute
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• v.19 no.5
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• pp.613-621
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• 2007

Due to the increasing significance of durability, much researches on carbonation, one of the major deterioration phenomena are carried out. However, conventional researches based on fully hardened concrete are focused on prediction of carbonation depth and they sometimes cause errors. In contrast with steel members, behaviors in early-aged concrete such as porosity and hydrates (calcium hydroxide) are very important and may be changed under carbonation process. Because transportation of deteriorating factors is mainly dependent on porosity and saturation, it is desirable to consider these changes in behaviors in early-aged concrete under carbonation for reasonable analysis of durability in long term exposure or combined deterioration. As for porosity, unless the decrease in $CO_2$ diffusion due to change in porosity is considered, the results from the prediction is overestimated. The carbonation depth and characteristics of pore water are mainly determined by amount of calcium hydroxide, and bound chloride content in carbonated concrete is also affected. So Analysis based on test for hydration and porosity is recently carried out for evaluation of carbonation characteristics. In this study, changes in porosity and hydrate $(Ca(OH)_2)$ under carbonation process are performed through the tests. Mercury Intrusion Porosimetry (MIP) for changed porosity, Thermogravimetric Analysis (TGA) for amount of $(Ca(OH)_2)$ are carried out respectively and analysis technique for porosity and hydrates under carbonation is developed utilizing modeling for behavior in early-aged concrete such as multi component hydration heat model (MCHHM) and micro pore structure formation model (MPSFM). The results from developed technique is in reasonable agreement with experimental data, respectively and they are evaluated to be used for analysis of chloride behavior in carbonated concrete.