• Smart Structures and Systems
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• v.33 no.5
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• pp.325-332
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• 2024

This study proposes a novel long short-term memory (LSTM)-based approach for predicting carbonation depth, with the aim of enhancing the durability evaluation of concrete structures. Conventional carbonation depth prediction relies on statistical methodologies using carbonation influencing factors and in-situ carbonation depth data. However, applying in-situ data for predictive modeling faces challenges due to the lack of time-series data. To address this limitation, an LSTM-based carbonation depth prediction technique is proposed. First, training data are generated through random sampling from the distribution of carbonation velocity coefficients, which are calculated from in-situ carbonation depth data. Subsequently, a Bayesian theorem is applied to tailor the training data for each target bridge, which are depending on surrounding environmental conditions. Ultimately, the LSTM model predicts the time-dependent carbonation depth data for the target bridge. To examine the feasibility of this technique, a carbonation depth dataset from 3,960 in-situ bridges was used for training, and untrained time-series data from the Miho River bridge in the Republic of Korea were used for experimental validation. The results of the experimental validation demonstrate a significant reduction in prediction error from 8.19% to 1.75% compared with the conventional statistical method. Furthermore, the LSTM prediction result can be enhanced by sequentially updating the LSTM model using actual time-series measurement data.

• Journal of the Korea Institute of Building Construction
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• v.24 no.1
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• pp.1-10
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• 2024

In-situ carbonation technology represents a form of mineral carbonation that integrates CO₂ into the fabrication process of cementitious construction materials, capturing CO₂ as calcium carbonate(CaCO₃) through a reaction between calcium ions(Ca²⁺) and CO₂ released during cement hydration. This investigation examines the application of in-situ carbonation technology to a variety of floor dry cement mortar formulations commonly used in local construction projects. It assesses the effects of varying the CO₂ injection flow rate and total volume of CO₂ injected. Additionally, the study evaluates the impact of reducing the quantity of cement used as a binder on the final product's quality.

• Computers and Concrete
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• v.31 no.3
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• pp.241-252
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• 2023

Corrosion of rebar is one of the major deteriorating mechanisms that affect the durability of reinforced concrete (RC) structures. The increase in CO₂ concentration in the atmosphere leads to early carbonation and deterioration due to corrosion in RC structures. In the present study, an attempt has been made to modify the existing carbonation depth prediction empirical model. The modified empirical model is verified from the carbonation data collected from selected RC structures of CSIR-SERC campus, Chennai and carbonation data available from the reported literature on in-situ RC structures. Attempt also made to study the carbonation depth in the laboratory specimens using oxygen permeability index (OPI) test. The carbonation depth measured from RC structures and laboratory specimens are compared with estimated carbonation depth obtained from OPI test data. The modified empirical model shows good correlation with measured carbonation depth from the identified RC structures and the reported RC structures from the literature. The carbonation depth estimated from OPI values for both in-situ and laboratory specimens show lesser percentage of error compared to measured carbonation depth. From the present investigation it can be said that the OPI test is the suitable test method for both new and existing RC structures and laboratory RC specimens.

• Bulletin of the Korean Chemical Society
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• v.30 no.11
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• pp.2567-2573
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• 2009

Carbonation of $Mg(OH)_2$ at 300 ${^{\circ}C}$ was studied by Infrared spectroscopy. Dehydroxylation and carbonation reactions were carried out in consecutive manner via 2-step procedure. Unidentate carbonates were produced only on defective surface of MgO in situ generated by dehydroxylation of $Mg(OH)_2$$Mg(OH)_2$${^{\circ}C}$ was proposed.

• Advances in concrete construction
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• v.12 no.6
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• pp.517-525
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• 2021

More underground structures are increasingly being constructed such as box culverts for electric power transmission, and the life extension of these structures is very important. It is well known that the steel embedded in concrete is usually invulnerable to corrosion because the high alkalinity of the pore solution in concrete generates a thin protective oxide layer on the surface of the steel. Recent observations in the field and experimental evidence have shown that even steel in concrete can be corroded through the carbonation reaction of cover concrete. Carbonation-induced corrosion in concrete may often occur in a high carbon dioxide environment. In this study, the risk of carbonation of underground box culverts in Korea was evaluated by measuring the car¬bonation rate and concrete cover depth in the field. Then, the carbonation-free service life for the cover depth of the steel was calcu¬lated with in situ information and Monte Carlo simulation. Additionally, an accelerated carbonation test for a cracked beam specimen was performed, and the effect of a crack on the service life of a box culvert was numerically investigated with Monte Carlo simulation based on experimental results.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.33 no.6
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• pp.226-233
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• 2023

In this study, the basic physical properties and microstructure of concrete interlocking blocks with amount of different CO₂ gas injection were analyzed according to determine the applicability of In-situ carbonation technology to construction secondary products. The amount of carbon dioxide gas injection was selected as 0, 0.1, 0.3, 0.5, 0.7 wt.% compared to cement amount. A lab-scale press equipment was designed to apply developed carbonation technology to real construction site. And mixer for stable CO₂ gas injection was designed. Using the designed devices, CO₂ gas injected samples were created and physical property of samples were performed. As a result of the physical property test, as the CO₂ injection amount increased to 0.3 %, it showed higher strength behavior compared to the original mix. And more than 0.5 % samples showed lower strength behavior than original sample, but they satisfied the standard of concrete interlocking block. This results were determined that CO₂ injection contributed to the creation of hydrates such as C-S-H. Therefore, the possibility of applying carbonation technology, which injects CO₂ during mixing, to various secondary construction products was confirmed.

• Journal of the Korea Concrete Institute
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• v.15 no.6
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• pp.902-912
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• 2003

The most common deteriorating processes of concrete structures are carbonation and chloride ion ingress. Many concrete structures have been suffered from chloride ions diffusion or carbonation induced reinforcement corrosion damage and many studies have been done on it. However, those studies were confined mostly to the single deterioration of carbonation or chloride attack only, although actual environment is rather of combined conditions. In case of many in-situ concrete structures, deterioration happened more for the case of combined attack than the single case of carbonation or chloride attack. In this paper, chloride profiles of carbonated concrete is predicted by considering two layer composite model, which is based on Fick's 2nd law. From the experimental result on combined deterioration of chloride and carbonation, it was examined that high chloride concentration was built up to 3∼5 mm over depth from carbonation depth. The analytical modeling of chloride diffusion was suggested to depict the relative influence of the carbonation depth. The diffusion coefficients of carbonation concrete and uncarbonated concrete with elapsed time were considered in this modeling.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.6
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• pp.30-40
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• 2014

The demand of underground structure such as box culvert for electric power transmission is increasing more and more, and the service life extension of these structures is very important. Recent observations in field and experimental evidences show that even steel in concrete can be corroded by carbonation reaction of cover concrete. Carbonation-induced corrosion in concrete may often occur in a high carbon dioxide environment. In this study, the risk of carbonation of box culverts in our nation was evaluated by measuring the carbonation rate and concrete cover depth in field. Then, the service life due to carbonation at the cover depth was calculated by in situ information and the Monte Carlo simulation in a probabilistic way. Additionally, the accelerated carbonation test for the cracked beam specimen was executed and the crack effect owing to the carbonation process on the service life of box culvert was numerically investigated via Monte Carlo simulation based on the experimental results.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 2011.10a
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• pp.157-164
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• 2011

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.4
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• pp.116-121
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• 2012

The construction of underground structures such as box culverts for electric power transmission is increasing more and more, and the life extension of these structures is very important. Carbonation-induced corrosion in concrete may often occur in a high carbon dioxide environment. In this study, the risk of carbonation of two concrete box culverts in an urban area was evaluated by measuring the carbonation rate and concrete cover depth. Then, the carbonation-free service life at the depth of the steel was calculated, based on in situ information, by the Monte Carlo simulation. The service life of box culvert due to carbonation was estimated over 250 years via Monte Carlo simulation.