• Journal of the Korea Concrete Institute
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• v.21 no.4
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• pp.449-455
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• 2009

The increase of industrial carbonic dioxide emissions has accelerated the carbonation of reinforced concrete structures, which drops off their durability. Although advanced countries have already taken safety control measures against the carbonation of RC structures, it is still difficult now to accurately predict the actual carbonation depth. Additionally, it requires much time and efforts. Recently, it is possible to get the data more rapidly through accelerated carbonation test with the $CO_2$ concentration of 100%. In this paper, the carbonation test results obtained by two test methods such as the normal carbonation test method and the accelerated carbonation test method, were compared to investigate the carbonation characteristics of fly ash concrete. The accelerated carbonation test on concrete specimens with the pre-curing age of 180 days was also carried out to examine the carbonation characteristics of fly ash concrete at long-term age. Consequently, fly ash concrete at early age was vulnerable to carbonation and however, its carbonation resistance at long-term ages was improved compared with OPC concrete.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.5
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• pp.27-33
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• 2014

Electrical resistivity of concrete can be measured in a more rapid and simple way for estimating durability of the concrete, however, carbonation causes a result of misleading for durability testing because carbonation leads to a significant reduction in the permeability and porosity of concrete. The purpose of this study is to estimate and quantify the effect of carbonation of concrete on a surface electrical resistivity measurement. Samples of three mixes with difference w/c were prepared and exposed in a carbonation chamber for 330 days. The results show that carbonation leads high electrical resistivity. The increase is substantial and has been shown to proportional to the extent of the carbonation by some of extent. The relationship between electrical resistivity and carbonation depth is taken in the study. Resistivity ratio of carbonated concrete to air concrete decreased significantly from the specific carbonation depth, however, resistivity ratio of carbonated concrete to air concrete had a linear relation with carbonation depth. From the relationship between electrical resistivity and carbonation depth, it is expected that the result should be subsequently used as a calibration curve for estimating carbonated concrete to overcome the interruption effect of carbonation on regular measurements of the electrical resistivity.

• 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 institute for structural maintenance and inspection
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• v.11 no.5
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• pp.81-88
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• 2007

Among deteriorations of concrete due to environmental exposure, carbonation problems of concrete structures have increased in urban and underground structures. But conventional carbonation-prediction equations that were proposed by foreign references, can not be applied directly to the prediction of carbonation for domestic concrete structures. The purpose of this study is to propose a prediction equation of carbonation depth by considering domestic exposure conditions of concrete structures. For the derivation of the equation, conventional carbonation-prediction equations are analyzed. Through considering the relationship between results of prediction equation and those of various domestic field survey data, the so-called correction factors for different domestic exposure condition of concrete structures are derived. Finally, a carbonation-prediction equation of concrete structures under domestic exposure conditions is proposed with consideration for concrete strength in core and correction factors.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2011.04a
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• pp.400-403
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• 2011

본 논문에서는 시차열중량분석법과 X-선 회절분석법을 이용한 원전콘크리트의 탄산화에 의한 열화도 평가를 진행하였으며 두 가지 정성적 분석방법을 이용한 반정량적 평가 방법을 개발하였다. 원자력발전소 건설에 사용된 동일한 콘크리트 배합을 사용한 시편을 촉진 탄산화 시험장치에 28, 56, 91, 180, 365일 기간에 걸쳐 노출시켜 탄산화를 진행하였으며 노출된 시편은 시차열중량분석법, X-선 회절분석법을 이용하여 탄산화에 따라 발생된 열화생성물의 양을 정성적으로 분석하였다. 그 결과, 탄산화로 인해 발생되는 Calcite의 양이 노출기간에 따라 점차적으로 증가되는 것이 확인되었으며, Calcite의 생성을 위해 이산화탄소와 반응하는 Portlandite의 양이 점차적으로 감소되는 것이 확인되었다. 본 논문에서는 위의 언급된 두 방법의 관계성을 통해 열화도 평가를 진행하였다.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.301-302
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• 2009

Uncertainties in carbonation process of concrete structures are treated by probability-based durability analysis for carbonation using Monte Carlo simulation technique. The results requires the minimum cover thickness of 53mm for 10% of corrosion probability under 4mm/$year^{0.5}$ of carbonation coefficient. The more researches on statistical properties of design variables may give reliable durability analysis/design methods for carbonation of concrete structures.

• Journal of the Korea Concrete Institute
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• v.22 no.2
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• pp.209-217
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• 2010

Recently, some mathematical models for the prediction on progress of carbonation of concrete were reported. These models take account for $CO_2$ diffusion and chemical reaction between $Ca(OH)_2$ and $CO_2$. Based on the assumption that $CO_2$ diffuses in the carbonation zone and reacts with $Ca(OH)_2$ at the outer face of carbonation zone and non-carbonation zone. In this study, a mathematical model to predict the progress of carbonation of concrete has been established based on the reducing concentration of $Ca(OH)_2$ in the carbonation progress zone, where $Ca(OH)_2$ reacts with $CO_2$ and $Ca(OH)_2$ and $CaCO_3$ coexist. Also, the prediction model of carbonation progress rate of concrete using the air permeability coefficient regarding to $CO_2$ diffusion is developed. As a result of this study, an expression, the model equation is obtained for the prediction of carbonation based on the time and interaction velocity between $CO_2$ and Ca(OH)$_2$ dependent air permeability coefficient. The prediction by the model satisfied the experimental data of the accelerated carbonation for painted concrete. Consequently, the model can predict the rate of carbonation and the potential service life of concrete structure exposed to atmosphere.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.2
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• pp.623-631
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• 2018

In this study, the degree of deterioration of concrete was investigated in the laboratory under conditions of carbonation and freeze-thaw cycling, which are the major causes of the deterioration of its performance. In this test, the carbonated concrete was subjected to combined freeze-thaw deterioration tests for up to 300 cycles, and its dynamic elastic modulus and compressive strength were measured. The evaluation of the effect of the water-binder ratio on normal concrete subjected to combined carbonization and freezing-thawing showed that its resistibility against such combined deterioration decreased more rapidly in the concrete with a water-binder ratio of 55 % compared with that having a water-binder ratio of 35 %. In the case where the concrete was blended with a mineral admixture consisting of fly ash and blast furnace slag at the same water-binder ratio, it showed an increase of its resistibility against combined deterioration.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.4
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• pp.259-266
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• 2018

In the work, the carbonation behavior and strength characteristics in cold-joint concrete are evaluated for OPC(Ordinary Portland Cement) and GGBFS(Ground Granulated Blast Furnace Slag)concrete considering three levels of curing age (28, 91 and 365 days). The compressive strength in GGBFS concrete is level of 86% of OPC concrete at the 91 days of curing period, but is level of 107% at 365 curing days due to hydration reaction. Carbonation velocities in both OPC and GGBFS concrete significantly decease after 91 curing days. The effect of cold joint on carbonation is evaluated to be small in GGBFS concrete. The increasing ratios of carbonation velocity in cold joint are 1.06 and 1.33 for 28-day and 365-day curing condition, respectively. However they decreases to 1.08 and 1.04 for GGBFS concrete for the same curing conditions.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.20 no.6
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• pp.575-582
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• 2008

Carbonation is one of major factors influencing on the durability of concrete structure. This paper investigates the effect of carbonation on the soundness of harbor concrete structure and quantifies the influence of carbonation based on in-situation data tested at 369 points in 69 harbor facilities. The relationships between carbonation depth and cover depth, and between carbonation depth and compressive strength are studied and the failure probability of durability, that is the initiation probability of steel corrosion, is evaluated on the basis of reliability concept. The in-situation test results showed that the ratio of carbonation depth to cover depth was less than 0.2, and the carbonation depth increased with age. In most cases, the failure probability of durability by carbonation was less than 10%. Therefore, it can be concluded that the influence of carbonation on the durability of harbor concrete structure is smaller than other factors deteriorating the durability of harbor concrete structure.