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This is an experiment on the effect of mixing time for alkali-activated cement (AAC) using a binder mixed with ground granulated blast furnace slag (slag) and fly ash (FA) in a ratio of 1:1 on the mechanical properties. The mixing method of ASTM C305 was used as the basic mixing method, and the following mixing method was changed. Simply adding the same mixing time and procedure, the difference in the order of mixing slag and FA, and controlling the amount of activator and mixed water were considered. As a result of the experiment, the addition of the same mixing time and procedure, pre-injection of slag, and high-alkali mixed water in which half of the activator and mixing water were mixed showed the highest mechanical properties and a dense pore structure. As a result, the design of a blending method that can promote the activation action of slag rather than FA at room temperature was effective in improving the mechanical properties of AAC. In addition, these blending factors showed a clearer effect as the concentration of the activator increased. Through the results of this experiment, it was shown that high-temperature curing, high fineness of the binder, or even changing the setting of the mixing method without the use of excessive activators can lead to an improvement of mechanical properties.
Taewan Kim; Choonghyun Kang. Investigation of the Effect of Mixing Time on the Mechanical Properties of Alkali-Activated Cement Mixed with Fly Ash and Slag. Materials 2021, 14, 2301 .
AMA StyleTaewan Kim, Choonghyun Kang. Investigation of the Effect of Mixing Time on the Mechanical Properties of Alkali-Activated Cement Mixed with Fly Ash and Slag. Materials. 2021; 14 (9):2301.
Chicago/Turabian StyleTaewan Kim; Choonghyun Kang. 2021. "Investigation of the Effect of Mixing Time on the Mechanical Properties of Alkali-Activated Cement Mixed with Fly Ash and Slag." Materials 14, no. 9: 2301.
This is an experimental study on the development of a low-carbon, eco-friendly cement containing a calcium sulfoaluminate expansive agent (CSAe), slag, and silica fume (SF). The cement to be developed has a low water/binder ratio (w/b) of 0.5 and is designed to be used for structural purposes, with focus on its mechanical performance. CSAe, slag, and SF were mixed at various mixing ratios. The main hydration product of the slag-based CSAe cement in the experiment was ettringite. Substituting less than 30% of CSAe showed a sufficient level of mechanical performance; that is, the material could be used as structural cement. SF controlled the excessive expansion of CSAe. However, since the developed slag-CSAe-SF cement has low early age (1 d) strength, follow-up research is needed for improvement.
Taewan Kim; Ki-Young Seo; Choonghyun Kang; Tak-Kee Lee. Development of Eco-Friendly Cement Using a Calcium Sulfoaluminate Expansive Agent Blended with Slag and Silica Fume. Applied Sciences 2021, 11, 394 .
AMA StyleTaewan Kim, Ki-Young Seo, Choonghyun Kang, Tak-Kee Lee. Development of Eco-Friendly Cement Using a Calcium Sulfoaluminate Expansive Agent Blended with Slag and Silica Fume. Applied Sciences. 2021; 11 (1):394.
Chicago/Turabian StyleTaewan Kim; Ki-Young Seo; Choonghyun Kang; Tak-Kee Lee. 2021. "Development of Eco-Friendly Cement Using a Calcium Sulfoaluminate Expansive Agent Blended with Slag and Silica Fume." Applied Sciences 11, no. 1: 394.
This study investigates the characteristics of alkali-activated slag cement using aluminium sulphate (ALS) as an activator. The alkalis NaOH and Na2SiO3 were used as additional activators (denoted by alkali) at 5% and 10% of the weight of the ground granulated blast furnace slag (GGBFS). Three types of activators were considered. The first was when ALS was used alone. For the second, ALS and 5% alkali were used together. The third was when ALS and 10% alkali were used. ALS was used at concentrations of 2%, 4%, 6%, 8%, and 10% based on binder weight. Experimental results show that when ALS was used as a sole activator, the activity of GGBFS was low and its strength was below 1 MPa. However, compressive strength was improved when 5% or 10% alkali and ALS were used at the same time. This was effective at improving mechanical and microstructural performance when used with an additional activator capable of forming a more alkaline environment than using ALS as a sole activator.
Taewan Kim; Sungnam Hong; Choonghyun Kang. The Effects of Aluminium Sulphate on Slag Paste Activated with Sodium Hydroxide and Sodium Silicate. Materials 2020, 13, 2286 .
AMA StyleTaewan Kim, Sungnam Hong, Choonghyun Kang. The Effects of Aluminium Sulphate on Slag Paste Activated with Sodium Hydroxide and Sodium Silicate. Materials. 2020; 13 (10):2286.
Chicago/Turabian StyleTaewan Kim; Sungnam Hong; Choonghyun Kang. 2020. "The Effects of Aluminium Sulphate on Slag Paste Activated with Sodium Hydroxide and Sodium Silicate." Materials 13, no. 10: 2286.
In this study, investigate the pore and strength characteristics of alkali-activated slag paste, using seawater and tapwater as the mixing water. The water/binder ratio is 0.45 and the activator is sodium hydroxide (NaOH). Activator concentrations of 2%, 4%, and 6% of the binder weight are used. This study measure the compressive strength and conduct X-ray diffraction (XRD), mercury-intrusion porosimetry (MIP), and scanning electron microscopy (SEM) to determine the cause of the increase in strength change and pore structure. The results indicate that the compressive strength between early and later ages improves with the use of seawater instead of tapwater. When seawater is used, C–S–H gel and Friedel's salt (FS) are observed as the hydration reactants. From the MIP measurements, when the NaOH concentration increases, the pore size and number of pores decrease to form a denser matrix. In particular, seawater samples increase the amount of gel pores (<0.1 μm).
Choonghyun Kang; Taewan Kim. Pore and strength characteristics of alkali-activated slag paste with seawater. Magazine of Concrete Research 2020, 72, 499 -508.
AMA StyleChoonghyun Kang, Taewan Kim. Pore and strength characteristics of alkali-activated slag paste with seawater. Magazine of Concrete Research. 2020; 72 (10):499-508.
Chicago/Turabian StyleChoonghyun Kang; Taewan Kim. 2020. "Pore and strength characteristics of alkali-activated slag paste with seawater." Magazine of Concrete Research 72, no. 10: 499-508.
This study is about the mechanical and microstructural properties of alkali-activated slag (AAS) paste using magnesium sulfate (MS) as an activator. MS is 2%, 4%, 6%, 8% and 10% contents of binder weight and water-binder ratio is 0.35. Compressive strength, X-ray diffraction, mercury-intrusion porosimetry, and thermal analysis were performed for analysis. The MS contents at which the maximum compressive strength appeared varied according to the measurement age. Hydration products affecting compressive strength and pore structure were ettringite and gypsum. As a result, the changes of ettringite and gypsum depending on the contents of MS have a great influence on the pore structure, which causes the change of compressive strength. The high MS contents increases the amount of gypsum in the hydration products, and the excess gypsum causes high expansion, which increases the diameter and amount of pores, thereby reducing the compressive strength.
Choonghyun Kang; Taewan Kim. Investigation of the Effects of Magnesium-Sulfate as Slag Activator. Materials 2020, 13, 305 .
AMA StyleChoonghyun Kang, Taewan Kim. Investigation of the Effects of Magnesium-Sulfate as Slag Activator. Materials. 2020; 13 (2):305.
Chicago/Turabian StyleChoonghyun Kang; Taewan Kim. 2020. "Investigation of the Effects of Magnesium-Sulfate as Slag Activator." Materials 13, no. 2: 305.
In bridge structures, concrete decks have a higher risk of damage than other components owing to the direct impact of traffic. This study aims to develop a comprehensive system for bridge inspection using passive infrared thermography (IRT). Experiments were conducted on a concrete specimen (assumed as the surface of the bridge deck) embedded artificial delaminations with different width-to-depth ratios (WTDRs). Both professional handheld IR camera (H-IRC) and a UAV mounted with an IR camera (UAV-IRC) were employed simultaneously to capture the surface temperature of the structure. The present work indicates that the passive IRT technique with an H-IRC can be used to detect delaminations located at depths of 4 cm or less from the structure surface if the WTDRs are not lesser than 1.9 for daytime and 2.5 for nighttime when testing on a sunny day. In addition, the larger the WTDR, the higher the temperature difference can be produced, thus delaminations could be observed more clearly. Furthermore, our study suggests that the concrete bridge deck inspection using passive IRT can produce appropriate results if the inspection is performed from 10:00 to 15:00 or from 19:30 to approximately 2:00 on a sunny day. Good agreement between the results obtained from tests using H-IRC and UAV-IRC was observed, which validates the application of UAV-IRC in real structure inspection.
Van Ha Mac; Quang Huy Tran; Jungwon Huh; Nhu Son Doan; Choonghyun Kang; Dongyeob Han. Detection of Delamination with Various Width-to-depth Ratios in Concrete Bridge Deck Using Passive IRT: Limits and Applicability. Materials 2019, 12, 3996 .
AMA StyleVan Ha Mac, Quang Huy Tran, Jungwon Huh, Nhu Son Doan, Choonghyun Kang, Dongyeob Han. Detection of Delamination with Various Width-to-depth Ratios in Concrete Bridge Deck Using Passive IRT: Limits and Applicability. Materials. 2019; 12 (23):3996.
Chicago/Turabian StyleVan Ha Mac; Quang Huy Tran; Jungwon Huh; Nhu Son Doan; Choonghyun Kang; Dongyeob Han. 2019. "Detection of Delamination with Various Width-to-depth Ratios in Concrete Bridge Deck Using Passive IRT: Limits and Applicability." Materials 12, no. 23: 3996.
This study applies a new method of mixing colloidal nano-silica (CNS). Previous studies have used powdered nano-silica or colloidal nano-silica and applied a binder weight substitution method. In this study, we tried to use ordinary Portland cement (OPC) as a binder and replace CNS with weight of mixing water. CNS was replaced by 10%, 20%, 30%, 40%, and 50% of the mixing water weight. The flow value, setting time, compressive strength, hydration reactant (X-ray diffractometer; XRD), pore structure (mercury intrusion porosimetry; MIP), thermal analysis, and scanning electron microscopy (SEM) analysis were performed. Experimental results show that the new substitution method improves the mechanical and microstructural properties through two effects. One is that the weight substitution of the mixing water shows a homogeneous dispersion effect of the nano-silica particles. The other is the effect of decreasing the w/b ratio when the CNS is substituted because the CNS is more dense than the mixing water. Therefore, we confirmed the applicability of mixing water weight replacement method as a new method of mixing CNS.
Taewan Kim; Sungnam Hong; Ki-Young Seo; Choonghyun Kang. Characteristics of Ordinary Portland Cement Using the New Colloidal Nano-Silica Mixing Method. Applied Sciences 2019, 9, 4358 .
AMA StyleTaewan Kim, Sungnam Hong, Ki-Young Seo, Choonghyun Kang. Characteristics of Ordinary Portland Cement Using the New Colloidal Nano-Silica Mixing Method. Applied Sciences. 2019; 9 (20):4358.
Chicago/Turabian StyleTaewan Kim; Sungnam Hong; Ki-Young Seo; Choonghyun Kang. 2019. "Characteristics of Ordinary Portland Cement Using the New Colloidal Nano-Silica Mixing Method." Applied Sciences 9, no. 20: 4358.
This study investigates the mechanical and microstructural properties of paste comprising ordinary Portland cement (OPC) added with polyaluminum chloride (PACl). The properties of the resulting mixture are analyzed using compressive strength, X-ray diffraction, scanning electron microscopy (SEM), mercury intrusion porosimetry, and thermogravimetric analysis. The results show that the addition of PACl improves the mechanical properties of OPC paste, that calcium-(aluminum)-silicate-hydrate (C-(A)-S-H) gel and Friedel's salt are the major products forming from the reaction with the aluminum and chloride ions in PACl, and that the portlandite content decreases. Moreover, the size and number of micropores decrease, and compressive strength increases. All these phenomena are amplified by increasing PACl content. SEM images confirm these findings by revealing Friedel's salt in the micropores. Thus, this work confirms that adding PACl to OPC results in a mixture with superior mechanical and microstructural properties.
Taewan Kim; Choonghyun Kang; Sungnam Hong; Ki-Young Seo. Investigating the Effects of Polyaluminum Chloride on the Properties of Ordinary Portland Cement. Materials 2019, 12, 3290 .
AMA StyleTaewan Kim, Choonghyun Kang, Sungnam Hong, Ki-Young Seo. Investigating the Effects of Polyaluminum Chloride on the Properties of Ordinary Portland Cement. Materials. 2019; 12 (20):3290.
Chicago/Turabian StyleTaewan Kim; Choonghyun Kang; Sungnam Hong; Ki-Young Seo. 2019. "Investigating the Effects of Polyaluminum Chloride on the Properties of Ordinary Portland Cement." Materials 12, no. 20: 3290.
The self-healing nature of concrete has been proved in many studies using various methods. However, the underlying mechanisms and the distinct area of self-healing have not been identified in detail. This study focuses on the limits of the area of self-healing. A bending specimen with a notch is used herein, and its flexural strength and stiffness before and after healing are compared and used for self-healing assessment. In addition, the neutral axis of the specimen was measured using successive strain gauges attached to the crack propagation part. Although the strength and stiffness of the concrete recovered after self-healing, the change in the location of the neutral axis before and after healing was insignificant, which indicates that physical recovery did not occur for once-opened crack areas.
Choonghyun Kang; Taewan Kim. Curable Area Substantiation of Self-Healing in Concrete Using Neutral Axis. Applied Sciences 2019, 9, 1537 .
AMA StyleChoonghyun Kang, Taewan Kim. Curable Area Substantiation of Self-Healing in Concrete Using Neutral Axis. Applied Sciences. 2019; 9 (8):1537.
Chicago/Turabian StyleChoonghyun Kang; Taewan Kim. 2019. "Curable Area Substantiation of Self-Healing in Concrete Using Neutral Axis." Applied Sciences 9, no. 8: 1537.
In recent years, several large earthquakes have caused the collapse of container cranes, which have resulted in halting of freighting, and significantly affected the economy. Some reports are concerned the uplift and derailment events of crane legs, and the collapse of the crane itself. In this study, the effects of different boundary conditions used in the numerical method are investigated for a container crane under seismic excitation. Three different boundary conditions are considered in terms of the connection of the crane’s legs (wheels) and the ground (rails), namely pin support (PIN), gap element (GAP), and Friction contact (FC) elements, by using the SAP2000 program for a typical container crane. Then, time history dynamic analyses are conducted using nine recorded ground motions. Dynamic behaviors of the container crane are studied in terms of the total base shear, portal drift, and relative displacement of legs, by investigating the three types of base boundary conditions. The results of the study show that when the intensity of earthquakes is large enough to create uplift and derailment events, the selection of the boundary condition model considerably affects the dynamic responses of the container crane. In addition, when uplift and derailment of the crane occur, the FC support condition is the most compatible with the real behavior of the crane. On the other hand, under low seismic excitation, there is no significant difference of the crane behavior according to the choice of boundary condition model.
Jungwon Huh; Van Bac Nguyen; Quang Huy Tran; Jin-Hee Ahn; Choonghyun Kang. Effects of Boundary Condition Models on the Seismic Responses of a Container Crane. Applied Sciences 2019, 9, 241 .
AMA StyleJungwon Huh, Van Bac Nguyen, Quang Huy Tran, Jin-Hee Ahn, Choonghyun Kang. Effects of Boundary Condition Models on the Seismic Responses of a Container Crane. Applied Sciences. 2019; 9 (2):241.
Chicago/Turabian StyleJungwon Huh; Van Bac Nguyen; Quang Huy Tran; Jin-Hee Ahn; Choonghyun Kang. 2019. "Effects of Boundary Condition Models on the Seismic Responses of a Container Crane." Applied Sciences 9, no. 2: 241.
Detecting subsurface delamination is a difficult and vital task to maintain the durability and serviceability of concrete structure for its whole life cycle. The aim of this work was to obtain better knowledge of the effect of depth, heating time, and rebar on the detectability capacity of delamination. Experimental tests were carried out on a concrete specimen in the laboratory using Long Pulsed Thermography (LPT). Six halogen lamps and a long wavelength infrared camera with a focal plane array of 640 × 480 pixels were used as the heat source and infrared detector, respectively. The study focused on the embedded imitation delaminations with the size of 10 cm × 10 cm × 1 cm, located at depths varying from 1 to 8 cm. The signal-to-noise ratio (SNR) was applied as a criterion to assess the detectability of delamination. The results of this study indicate that as the provided heating time climbed, the SNR increased, and the defect could be identified more clearly. On the other hand, when using the same heating regime, a shallow delamination displayed a higher SNR than a deeper one. The moderate fall of the SNR in the case of imitating defect located below reinforced steel was also observed. The absolute contrast was monitored to determine the observation time, and the nondimensional prefactor k was empirically proposed to predict the depth of delamination. The mean absolute percentage error (MAPE) was used to quantitatively evaluate the difference between forecasted and real depth, which evaluation confirmed the high reliability of the estimated value of the prefactor k.
Jungwon Huh; Van Ha Mac; Quang Huy Tran; Ki-Yeol Lee; Jong-In Lee; Choonghyun Kang. Detectability of Delamination in Concrete Structure Using Active Infrared Thermography in Terms of Signal-to-Noise Ratio. Applied Sciences 2018, 8, 1986 .
AMA StyleJungwon Huh, Van Ha Mac, Quang Huy Tran, Ki-Yeol Lee, Jong-In Lee, Choonghyun Kang. Detectability of Delamination in Concrete Structure Using Active Infrared Thermography in Terms of Signal-to-Noise Ratio. Applied Sciences. 2018; 8 (10):1986.
Chicago/Turabian StyleJungwon Huh; Van Ha Mac; Quang Huy Tran; Ki-Yeol Lee; Jong-In Lee; Choonghyun Kang. 2018. "Detectability of Delamination in Concrete Structure Using Active Infrared Thermography in Terms of Signal-to-Noise Ratio." Applied Sciences 8, no. 10: 1986.
Ship-to-shore (STS) container gantry cranes, used at terminals for loading and unloading containers from a ship, are an important part of harbor structures. The size and weight of modern STS container cranes are increasing to satisfy the demand for bigger ships. This is expected to result in more lateral load when excited by seismic motions. The existing Korean STS container cranes did not behave properly during several recent moderate earthquakes in South Korea. Typical Korean STS container cranes must be checked for the earthquake-resistant capacity. In this research, two nonlinear static analyses procedures, also known as pushover analyses, commonly used for seismic design of buildings, namely, capacity spectrum method and equivalent linearization method, are comprehensively studied to check their suitability for studying seismic behavior of STS cranes. Results obtained by these two nonlinear static analysis methods are then compared with the results obtained by nonlinear time-history analyses of the STS cranes by exciting them with nine recorded earthquake time histories around worldwide. The behaviors of the cranes are analyzed in terms of the total base shear, drift, and base uplift. The comparisons indicate that the nonlinear static methods can be appropriate for estimating the total base shear and drift of the portal frame of a container crane. The pushover analyses also provide information on performance levels as defined in ASCE/SEI 41-13, of a typical Korean STS container crane. Furthermore, it is observed that the uplift response of the crane is strongly influenced by the duration of an earthquake.
Quang Huy Tran; Jungwon Huh; Van Bac Nguyen; Achintya Haldar; Choonghyun Kang; Kyeong Min Hwang. Comparative Study of Nonlinear Static and Time-History Analyses of Typical Korean STS Container Cranes. Advances in Civil Engineering 2018, 2018, 1 -13.
AMA StyleQuang Huy Tran, Jungwon Huh, Van Bac Nguyen, Achintya Haldar, Choonghyun Kang, Kyeong Min Hwang. Comparative Study of Nonlinear Static and Time-History Analyses of Typical Korean STS Container Cranes. Advances in Civil Engineering. 2018; 2018 ():1-13.
Chicago/Turabian StyleQuang Huy Tran; Jungwon Huh; Van Bac Nguyen; Achintya Haldar; Choonghyun Kang; Kyeong Min Hwang. 2018. "Comparative Study of Nonlinear Static and Time-History Analyses of Typical Korean STS Container Cranes." Advances in Civil Engineering 2018, no. : 1-13.
The self-healing performance of PE and PVA concrete was evaluated, by using the three-point bending test with a notch. Four different crack inducement days were applied (7, 28, 49, and 91 days), and the same 21 days of healing period were applied to each case. The self-healing environments were in 20°C water, and in the curing room with 20°C temperature and 60% humidity. The flexural strength and the initial flexural stiffness of before and after healing were compared. As a result, both the strength recovery effect and the stiffness recovery effect decreased with the delay of crack inducement, and specimens in the water environment showed higher healing effect than those in the air environment. PVA fiber showed a relatively greater recovery effect than PE fiber.
Choonghyun Kang; Jungwon Huh; Quang Huy Tran; Kiseok Kwak. Evaluation of Self-Healing Performance of PE and PVA Concrete Using Flexural Test. Advances in Materials Science and Engineering 2018, 2018, 1 -10.
AMA StyleChoonghyun Kang, Jungwon Huh, Quang Huy Tran, Kiseok Kwak. Evaluation of Self-Healing Performance of PE and PVA Concrete Using Flexural Test. Advances in Materials Science and Engineering. 2018; 2018 ():1-10.
Chicago/Turabian StyleChoonghyun Kang; Jungwon Huh; Quang Huy Tran; Kiseok Kwak. 2018. "Evaluation of Self-Healing Performance of PE and PVA Concrete Using Flexural Test." Advances in Materials Science and Engineering 2018, no. : 1-10.
Choonghyun Kang; Jungwon Huh; Kiseok Kwak; Bang Yeon Lee. Assessment of Self-Healing Performance of Fly ash Concrete Incorporating PE Fiber and PVA Fiber Using Flexural Test. Journal of the Korea Concrete Institute 2018, 30, 157 -166.
AMA StyleChoonghyun Kang, Jungwon Huh, Kiseok Kwak, Bang Yeon Lee. Assessment of Self-Healing Performance of Fly ash Concrete Incorporating PE Fiber and PVA Fiber Using Flexural Test. Journal of the Korea Concrete Institute. 2018; 30 (2):157-166.
Chicago/Turabian StyleChoonghyun Kang; Jungwon Huh; Kiseok Kwak; Bang Yeon Lee. 2018. "Assessment of Self-Healing Performance of Fly ash Concrete Incorporating PE Fiber and PVA Fiber Using Flexural Test." Journal of the Korea Concrete Institute 30, no. 2: 157-166.
The active thermography technique is one of the most effective nondestructive tests for evaluating subsurface delaminations in concrete structures. The limitation of this method, which has been studied for some time, is that the width of the smallest detectable defect should be at least two times larger than its depth. However, controversy on this matter remains for concrete material with largely uncertain homogeneity, although the development of the infrared (IR) detector technology improved the above-mentioned limitation. In this study, the pulsed thermography (PT) technique is therefore conducted in the laboratory to investigate the detectability of delaminations with the width-to-depth ratio (w2d) ranging from 1.0 to 7.9 by using a long IR wavelength detector with a focal plane array of 640 \(\times \) 480 pixels. The study focuses on the w2d ratio lower than 2.0. A concrete specimen was made with 12 embedded simulated delaminations having different sizes and depths. The results showed that a combination of PT and pulsed phase thermography can be used to detect delaminations with a w2d ratio equal or greater than 1.25. In addition, the absolute contrast above the delamination increases with the higher w2d ratio, indicating that even for a relatively deep delamination, it is still detectable if a delamination is provided by appropriate heat energy and its size is sufficiently large. Finally, the study also indicates that as the amount of heating energy provided is increased, the greater accuracy in predicting the depth can be obtained.
Quang Huy Tran; Jungwon Huh; Choonghyun Kang; Bang Yeon Lee; In-Tae Kim; Jin-Hee Ahn. Detectability of Subsurface Defects with Different Width-to-Depth Ratios in Concrete Structures Using Pulsed Thermography. Journal of Nondestructive Evaluation 2018, 37, 32 .
AMA StyleQuang Huy Tran, Jungwon Huh, Choonghyun Kang, Bang Yeon Lee, In-Tae Kim, Jin-Hee Ahn. Detectability of Subsurface Defects with Different Width-to-Depth Ratios in Concrete Structures Using Pulsed Thermography. Journal of Nondestructive Evaluation. 2018; 37 (2):32.
Chicago/Turabian StyleQuang Huy Tran; Jungwon Huh; Choonghyun Kang; Bang Yeon Lee; In-Tae Kim; Jin-Hee Ahn. 2018. "Detectability of Subsurface Defects with Different Width-to-Depth Ratios in Concrete Structures Using Pulsed Thermography." Journal of Nondestructive Evaluation 37, no. 2: 32.
Jungwon Huh; Thai Son Le; Choonghyun Kang; Kiseok Kwak; Inn-Joon Park. A probabilistic fragility evaluation method of a RC box tunnel subjected to earthquake loadings. Journal of Korean Tunnelling and Underground Space Association 2017, 19, 143 -159.
AMA StyleJungwon Huh, Thai Son Le, Choonghyun Kang, Kiseok Kwak, Inn-Joon Park. A probabilistic fragility evaluation method of a RC box tunnel subjected to earthquake loadings. Journal of Korean Tunnelling and Underground Space Association. 2017; 19 (2):143-159.
Chicago/Turabian StyleJungwon Huh; Thai Son Le; Choonghyun Kang; Kiseok Kwak; Inn-Joon Park. 2017. "A probabilistic fragility evaluation method of a RC box tunnel subjected to earthquake loadings." Journal of Korean Tunnelling and Underground Space Association 19, no. 2: 143-159.
Micro cracks occurring in concrete around tensile rebar is well known latent damage phenomenon. These micro cracks develop, and can be detected after reaching the surface of the concrete. Detection of these cracks before they are fully formed is preferable, but observing the whole crack structure is difficult. Another problem is repairing micro cracks under the concrete surface. The autogenous ability of bond cracks along rebar was evaluated using the air permeability test. Air permeability coefficients were measured before and after tensile loading, and experimental air permeability coefficients became larger near cracks along rebar as a result of tensile loading. Recuring for 28 days after tensile loading made the air permeability coefficients smaller, but this restriction only occurred during water recuring. Observation of crack patterns helped the understanding of change in the air permeability coefficients. Several small cracks along rebar were observed after tensile loading, and most cracks along rebar were not found after water recuring. On the other hand, the crack pattern did not change after air recuring. These results indicate that bond cracks along rebar can be closed by autogenous healing, and cause the air permeability coefficients.
Choonghyun Kang; Minoru Kunieda. Evaluation and Observation of Autogenous Healing Ability of Bond Cracks along Rebar. Materials 2014, 7, 3136 -3146.
AMA StyleChoonghyun Kang, Minoru Kunieda. Evaluation and Observation of Autogenous Healing Ability of Bond Cracks along Rebar. Materials. 2014; 7 (4):3136-3146.
Chicago/Turabian StyleChoonghyun Kang; Minoru Kunieda. 2014. "Evaluation and Observation of Autogenous Healing Ability of Bond Cracks along Rebar." Materials 7, no. 4: 3136-3146.