• Computers and Concrete
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• 제10권3호
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• pp.219-229
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• 2012

Carbonation is a widespread degradation of concrete and may be coupled with more severe degradations. An experimental investigation was carried out to study the effect of carbonation on chloride ion diffusion of concrete. The characteristic of concrete after carbonation was measured, such as carbonation depth, strength and pore structure. Results indicated that carbonation depth has a good linear relation with square root of carbonate time, and carbonation can improve compressive strength, but lower flexural strength. Results about pore structure of concrete before and after carbonation have shown that carbonation could cause a redistribution of the pore sizes and increase the proportion of small pores. It also can decrease porosities, most probable pore size and average pore diameters. Chloride ion diffusion of concrete after carbonation was studied through natural diffusion method and steady state migration testing method respectively. It is supposed that the chloride ion concentration of carbonation region is higher than that of the sound region because of the separation of fixed salts, and chloride ion diffusion coefficient was increased due to carbonation action evidently.

• International Journal of Concrete Structures and Materials
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• 제7권2호
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• pp.119-125
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• 2013

Carbonation is a natural ageing process for cement. This study focuses on how the carbonation rate varies with selected hydration times and atmospheric conditions during the early stages of reacting dried cement paste. Diffuse reflection Fourier transform infrared spectroscopy is shown to be a suitable technique to monitor the formation of carbonates in cement. Combined with a previously developed freeze drying technique, carbonation can be studied at specific hydration stages. In ambient air both calcium hydroxide and calcium silicate hydrate (C-S-H) in cement are carbonated. Increased hydration time enhances the carbon dioxide uptake, which indicates that the calcium in the hydration products reacts more easily than the calcium in the clinker phase. In a humid $CO_2$ atmosphere, the carbonation process is so pronounced that it decomposes C-S-H into calcium carbonate and silica. In a moist $N_2$ atmosphere no carbonation occurs, but the sulfate chemistry of the cement seems to be affected due to the formation of ettringite.

• Corrosion Science and Technology
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• 제6권4호
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• pp.186-192
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• 2007

Carbonation is one of the most important factors causing the corrosion of reinforcement concrete. Nevertheless, experimental studies on the concrete carbonation have not been carried out sufficiently because of the slow process of carbonation process. Therefore, this study adopts an experimental system exploiting a vacuum instrument that has been recently developed to accelerate carbonation instead of existing experimental system to conduct rapid carbonation tests on Portland cement and fly-ash cement concretes. Test results revealed that, compared to water-cement ratio of 40%, the carbonation depth increases from 103% to 138% for an increase of water-cement ratio from 45% to 60%. These results are larger than the carbonation depths obtained by mathematical model, and such difference is increasing with larger water-cement ratios. The results also indicated that larger fly-ash contents lead to sharp increase of the carbonation depth, which is in agreement with previous experimental researches. The adoption of the new accelerated carbonation test system enabled to shorten effectively the time required to produce experimental data compared to the existing carbonation test method. The experimental data obtained in this study together with ongoing acquisition of data using the new carbonation test method are expected to contribute in the understanding of the carbonation process of concrete structures in Korea.

• Structural Engineering and Mechanics
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• 제63권1호
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• pp.55-64
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• 2017

The paper concerns concrete carbonation, the phenomena that occurs in every type of climate, especially in urban-industrial areas. In European Standards, including Eurocode (EC) for concrete structures the demanded durability of construction located in the conditions of the carbonation threat is mainly assured by the selection of suitable thickness of reinforcement cover. According to EC0 and EC2, the thickness of the cover in the particular class of exposure depends on the structural class/category and concrete compressive strength class which is determined by cement content and water-cement ratio (thus the quantitative composition) but it is not differentiated for various cements, nor additives (i.e., qualitative composition), nor technological types of concrete. As a consequence the selected thickness of concrete cover is in fact a far estimation - sometimes too exaggerated (too safe or too risky). The paper presents the elaborated "self-terminated carbonation model" that includes abovementioned factors and enables to indicate the maximal possible depth of carbonation. This is possible because presented model is a hyperbolic function of carbonation depth in time (the other models published in the literature use the parabolic function that theoretically assume the infinite increase of carbonation depth value). The paper discusses the presented model in comparison to other models published in the literature, moreover it contains the algorithm of concrete cover design with use of the model as well as an example of calculation of the cover thickness.

• Advances in concrete construction
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• 제17권5호
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• pp.245-255
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• 2024

The problem of carbonation-induced corrosion has become a concern in recent times, especially in the 21^st century, due to the increase in global temperatures and carbon dioxide (CO₂) concentration in the atmosphere possessing a significant threat to the durability of reinforced concrete (RC) structures worldwide, especially in inland tropical regions where carbonation is the most significant concrete degradation mechanism. Therefore, a study was conducted to predict the impact of global warming on the carbonation of RC structures in Lusaka, Zambia, and Tokyo, Japan. The Impact was estimated based on a carbonation meta-model that applies the analytic solution of Fick's 1st law using literature-based concrete mix design data and forecasted local temperature and CO₂ concentration data over a 100-year period with relative humidity assumed constant. The results showed that CO₂ diffusion increased between 17-31%, effecting a 40-45% rise in carbonation coefficient and a significant reduction in corrosion initiation time of 50-52% in the two cities. Moreover, for the same water-cement ratio, Lusaka showed almost twice higher carbonation coefficient values and one third shorter corrosion initiation time compared to Tokyo, mainly due to its higher temperature and low relative humidity. Additionally, the carbonation propagation depth at the end of 100 years was between 12-22 mm in Tokyo and 18-40 mm in Lusaka. These findings indicate that RC structures in these cities are at risk of rapid deterioration, especially in Lusaka, where they are more vulnerable.

• Corrosion Science and Technology
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• 제11권5호
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• pp.157-164
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• 2012

In first experiment series, this paper is devoted for examining progress of reinforcement corrosion due to carbonation in concrete and to quantify uncarbonation depth to protect reinforcement from corroding. The tolerance of cover depth should be considered in order to prevent carbonation-induced corrosion. From the relationship between the weight loss of reinforcement and corrosion current density for a given time, therefore, the tolerance of cover depth to prevent carbonation-induced corrosion is computed. It is observed that corrosion occurs when the distance between carbonation front and reinforcement surface (uncarbonated depth) is smaller than 5 mm.As a secondary purpose of this study, it is investigated to examine the interaction between carbonation and chloride penetration and their effects on concrete. This was examined experimentally under various boundary conditions. For concrete under the double condition, the risk of deterioration due to carbonation was not severe. However, it was found that the carbonation of concrete could significantly accelerate chloride penetration. As a result, chloride penetration in combination with carbonation is a serious cause of deterioration of concrete.

• Advances in concrete construction
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• 제11권5호
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• pp.367-374
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• 2021

The present study investigated the effect of the combined carbonation and steam curing on the physicochemical properties and CO₂ uptake of the Portland cement concrete. Four different curing regimes were adopted during the initial 10 h of curing to evaluate the potential of carbonation curing as an alternative to conventional steam curing in the precast concrete industry from environmental and practical viewpoints. Four combinations of carbonation and steam curing conditions were applied as curing regimes to the samples at an early age. The test results indicated that the samples treated with the combined carbonation and steam curing exhibited higher early strength development compared to the other samples, signifying that carbonation curing can reduce the production time of precast concrete. Furthermore, the CO₂ uptake capacity of the samples was calculated and found to be as high as 18% with respect to the mass of the paste samples. Hence, the simultaneous utilization of steam and CO₂ for the fabrication of precast concrete members has the potential to make precast concrete greener and more cost-effective.

• 한국산업융합학회 논문집
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• 제23권6_2호
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• pp.1111-1117
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• 2020

In this study, the carbonation characteristics of concrete according to the mixture of OLED waste glass were evaluated. Replacement capacities of OLED waste glass were 0%, 10%, 20%, and 30% of cement, and they were named OG 0, OG 10, OG 20, and OG 30. As a result of the compressive strength test, OG 0 without replacing OLED waste glass showed high intensity until the 14th. However, the higher the replacement rate of OLED waste glass, the higher the compressive strength of 28 days. In addition, the speed of carbonation was faster with the higher the replacement rate of OLED waste glass, and the accelerated carbonation experiment was about three times faster than the natural carbonation test. In conclusion, the carbonation characteristics of OLED concrete are expected to be positive in terms of atmospheric CO2 absorption.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2016년도 춘계 학술논문 발표대회
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• pp.207-208
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• 2016

The most important things for the production of recycled aggregates are saving energy, suppressing the generation of by-product fine particles and sustaining the performance of concrete. As solutions, this study proposes this technology of improving the performance of recycled aggregates through forced carbonation.1) It is to stimulate and carbonate the bond paste part that causes the deterioration of recycled aggregates. Particularly, the purpose of this technology is to fill and chemically stabilize pores inside the bond paste, further improving the quality of recycled aggregates with a decreased absorption rate and an enhanced aggregate strength. Ultimately, it is possible to obtain a carbonation model, depending on the paste ratio and particle-size distribution of recycled aggregates. Moreover, by calculating the optimum carbonation period through the verification of this carbonation model, it is possible to examine how much the strength is improved by the reformation of recycled aggregated.

• International Journal of Concrete Structures and Materials
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• 제5권1호
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• pp.11-18
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• 2011

Carbonation in RC (reinforced concrete) structure is considered as one of the most critical deteriorations in urban cities. Although RC column has one mix condition, carbonation depth is measured spatially differently due to its various environmental and internal conditions such as sound, cracked, and joint concrete. In this paper, field investigation was performed for 27 RC columns subjected to carbonation for eighteen years. Through this investigation, carbonation distribution in sound, cracked, and joint concrete were derived with crack mappings. Considering each related area and calculated PDF (probability of durability failure) of sound, cracked, and joint concrete through Monte Carlo Simulation (MCS), repairing timings for RC columns are derived based on several IPDF (intended probability of durability failure) of 1, 3, and 5%. The technique of equivalent probability including carbonation behaviors which are obtained from different conditions can provide the reasonable repairing strategy and the priority order for repairing in a given traffic service area.