• 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 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 the Korean Institute of Gas
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• v.18 no.2
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• pp.73-80
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• 2014

The objective of this paper is to assess the service life and retrain methods of specimens, which were subjected to carbonation attack, obtained from mix proportion of Sam-cheok LNG storage tank under construction. As the results, accelerated-carbonation penetration depths of 7, 28, 56 ages indicated 4.45, 9.19, 13.37mm, and even considering for cover depths of steel of LNG storage tank under real operation, it was enough. In addition, with carbonation velocity coefficient calculated by carbonation penetration depths, the service life to design cover depth(70, 80, 90, 100mm) of PC outer tank of LNG storage tank was 779, 1017, 1287, 1589 years and 466, 609, 771, 951 years, respectively, considering the $CO_2$ concentration in air which account for the 0.03% and 0.05%. Also, the restrain methods to carbonation attack were feasible through controlling the factors affecting the changes of hydration products such as $Ca(OH)_2$, ion composition in pore solution and matter mobility of organization structures within hardened concrete.

• Proceedings of the Korea Concrete Institute Conference
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• 2010.05a
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• pp.221-222
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• 2010

In this study an expression is obtained the model equation for the prediction of carbonation based on the time and interaction velocity between $CO_2$ and $Ca(OH)_2$ diffusion coefficient.

• 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.20 no.4
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• pp.111-119
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• 2016

Rebound hammer test, SonReb method and concrete core test are most useful testing methods for estimate the concrete compressive strength of deteriorated concrete structures. But the accuracy of the NDE results on the existing structures could be reduced by the effects of the uncertainty of nondestructive test methods, material effects by aging and carbonation, and mechanical damage by drilling of core. In this study, empirical procedure for verifying the in-situ compressive strength of concrete is suggested through the probabilistic analysis on the 268 data of rebound and ultra-pulse velocity and core strengths obtained from 106 bridges. To enhance the accuracy of predicted concrete strength, the coefficients of core strength, and surface hardness caused by ageing or carbonation was adopted. From the results, the proposed equation by KISTEC and the estimation procedures proposed by authors is reliable than previously suggested equation and correction coefficient.

• Journal of the Korea Institute of Building Construction
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• v.23 no.3
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• pp.285-293
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• 2023

In this research, we embarked on a meticulous analysis of the challenges inherent in real-world scenarios relating to the durability design standards of engineered concrete structures and the assessment of carbonation durability in concrete guidelines. Our investigation brought to light substantial issues concerning constructability and quality assurance. The genesis of these problems is the exclusive application of prescribed strength to exterior walls, neglecting other elements to facilitate smoother licensing procedures. While this methodology aims to mitigate financial constraints in alignment with enhanced standards, it invariably invites complications. Furthermore, it is imperative to resolve the uncertainty surrounding durability evaluations by establishing a clear and definitive objective. Alongside this, actionable steps must be formulated to forestall the emergence of fissures between the floors of residential buildings, particularly apartment complexes. It is equally essential to tackle issues connected to application by devising a comprehensive management strategy for potential cracking during the phase of maintenance.

• The Journal of the Korea Contents Association
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• v.14 no.12
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• pp.999-1009
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• 2014

In this paper, $CO_2$ emission and storage amount are evaluated for real RC (Reinforced Concrete) underground structure considering $CO_2$ amount including material manufacturing, moving, and construction, repairing timing stage regarding extended service life. Four mix proportions with mineral admixtures are prepared and $CO_2$ diffusion coefficient are obtained based on a micro modeling. Referred to carbonation durability limit state, $CO_2$ emission and storage amount are evaluated, which shows higher initial $CO_2$ emission is caused due to larger unit content of cement and the storage increases with more rapid carbonation velocity. Furthermore various $CO_2$ concentration is adopted for simulation of $CO_2$ evaluation including measured $CO_2$ concentration (600ppm). With higher concentration of $CO_2$ outside, carbonation velocity increases. In order to reduce $CO_2$ emission through entire service life, reducing initial $CO_2$ emission through mineral admixture like fly ash is more effective than increasing $CO_2$ storage through OPC since $CO_2$ is significantly emitted under manufacturing OPC and $CO_2$ storage in cover concrete of RC structure is not effective considering initial concrete amount in construction.

• Journal of the Korea Concrete Institute
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• v.17 no.5 s.89
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• pp.793-801
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• 2005

This study investigates fundamental properties of recycled aggregate concrete which incorporated 100% recycled coarse aggregate and various amount of recycled fine aggregate. In addition, for the purpose of the improvement of long term strength and durability, a part of cement was replaced with fly ash. Compressive strength and resistance to chloride ion penetration and carbonation were investigated. When the coarse aggregate was completely replaced with the recycled the replacement ratio of the fine aggregate with the recycled was recommended to be limited below 60% in the consideration of strength. The strength of the steam-cured specimen was very comparable to the wet-cured at 28 days. As fly ash content increased the resistance to chloride ion penetration was increased. The chloride ion penetrability based on the charge passed was found to be low at 21 days and very low at 56 days, respectively. Carbonation depth and carbonation velocity coefficient increased as the fly ash content increased and the relationship between the carbonation depth and recycled fine aggregate replacement ratio was not clear. Up to 28days, however, the measured carbonation depth was mostly less than 10mm which could be considered as low.

• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.4
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• pp.520-527
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• 2020

Hwangtoh is the rich resource that accounts for about 15.0% of the domestic soil, and can be used as the admixture of concrete with Pozzolan characteristics if activated by rapidly freezing after burning with high temperature. In this study, the mortar curbs containing active hwangtoh were produced, based on the mixture for the mortar curbs sold on the market. The substitution rate of active hwangtoh were considered 10.0% and 25.0%, and the test items were selected to compressive and flexural strength tests, freezing/thawing resistance tests, accelerated carbonation tests, and accelerated chloride diffusion tests. In the results of the mechanical performance, it was showed that the highest strength was evaluated in OPC mixture, and the increase in strength was small by the increase of age, which was believed to be due to the fact that most of the strength in each mixture was created in three days of steam curing. The results of the freezing/thawing tests for 28 aged days showed the reduction rate of compressive strength was 85.0% or higher for all specimen, meeting the criteria presented. The accelerated carbonation tests were carried out on the specimen at 28 days of age, and the results showed that the mortar with active hwangtoh had lower carbonation resistance performance than mortar with OPC. The passed charge of each mixture was assessed in accordance with ASTM C 1202 on 28 and 91 aged days. The OPC mixture had "Low" rate and the mortar with active hwangtoh had "Moderate" rate. So it was thought that the mortar with active hwangtoh had appropriate resistance performance for chloride attack.