• Magazine of the Korea Concrete Institute
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• v.16 no.1 s.78
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• pp.96-103
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• 2004

• Geomechanics and Engineering
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• v.34 no.1
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• pp.51-67
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• 2023

In this research, the degradation rate of physical properties of the Angouran pit bedrock (calc-schist) is first investigated under the specific numbers of freeze-thaw (F-T) cycles. Then, the durability of calc-schist specimens against the F-T cycle number (N) is examined considering the mechanical parameters, and using the decay function and half-time techniques. For this purpose, point load strength (I_S(50)), second durability index (I_d2), Brazilian tensile strength (BTS), and compressive (V_P) and shear (V_S) wave velocities of calc-schist specimens are measured after 0, 7, 15, 40, and 75 N. For comparing the degradation rate of mechanical properties of available rock types on the Angouran mine walls, these tests are also carried out on the limestone and amphibolite schist specimens beside the calc-schist. According to test results, the exponential regression models are developed between the mechanical parameters of rock specimen's and N variable. Also, the long-term durability of each rock type versus N is studied using the decay function and half-time techniques. Results indicated that the degradation rate differs for the above rock types in which amphibolite schist and calc-schist specimens have the highest and least resistance against the N, respectively. The obtained results from this study can play a key role in the optimal design of the mine's final walls.

• Pediatric Gastroenterology, Hepatology & Nutrition
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• v.24 no.1
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• pp.7-18
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• 2021

Purpose: The long-term efficacy and safety of infliximab (IFX) in children with ulcerative colitis (UC) have not been well-evaluated. Here, we reviewed the long-term durability and safety of IFX in our single center pediatric cohort with UC. Methods: This retrospective study included 20 children with UC who were administered IFX. Results: For induction, 5 mg/kg IFX was administered at weeks 0, 2, and 6, followed by every 8 weeks for maintenance. The dose and interval of IFX were adjusted depending on clinical decisions. Corticosteroid (CS)-free remission without dose escalation (DE) occurred in 30% and 25% of patients at weeks 30 and 54, respectively. Patients who achieved CS-free remission without DE at week 30 sustained long-term IFX treatment without colectomy. However, one-third of the patients discontinued IFX treatment because of a primary nonresponse, and one-third experienced secondary loss of response (sLOR). IFX durability was higher in patients administered IFX plus azathioprine for >6 months. Four of five patients with very early onset UC had a primary nonresponse. Infusion reactions (IRs) occurred in 10 patients, resulting in discontinuation of IFX in four of these patients. No severe opportunistic infections occurred, except in one patient who developed acute focal bacterial nephritis. Three patients developed psoriasis-like lesions. Conclusion: IFX is relatively safe and effective for children with UC. Clinical remission at week 30 was associated with long-term durability of colectomy-free IFX treatment. However, approximately two-thirds of the patients were unable to continue IFX therapy because of primary nonresponse, sLOR, IRs, and other side effects.

• International Journal of Highway Engineering
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• v.15 no.1
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• pp.1-9
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• 2013

PURPOSES: The purpose of this study is to evaluate physical properties, durability, fatigue resistance, and long-term performance of poly-urethane concrete (PU) which can be possible application of thin layer on long-span orthotropic steel bridge and to check structural stability of bridge structure. METHODS : Various tests of physical properties, such as flexural strength, tensile strength, bond strength and coefficient of thermal expansion tests were conducted for physical property evaluation using two types of poly urethane concrete which have different curing time. Freezing and thawing test, accelerated weathering test and chloride ion penetration test were performed to evaluate the effect of exposed to marine environment. Beam fatigue test and small scale accelerated pavement test were performed to assess the resistance of PU against fatigue damage and long-term performance. Structural analysis were conducted to figure out structural stability of bridge structure and thin bridge deck pavement system. RESULTS: The property tests results showed that similar results were observed overall however the flexural strength of PUa was higher than those of PUb. It was also found that PU materials showed durability at marine environment. Beam fatigue test results showed that the resistances of the PUa against fatigue damage were two times higher than those of the PUb. It was found form small scale accelerated pavement test to evaluate long-term performance that there is no distress observed after 800,000 load applications. Structural analysis to figure out structural stability of bridge structure and thin bridge deck pavement system indicated that bridge structures were needed to increase thickness of steel deck plate or to improve longitudinal rib shape. CONCLUSIONS: It has been known that the use of PU can be positively considered to thin layer on long-span orthotropic steel bridge in terms of properties considered marine environment, resistance of fatigue damage and long-term performance.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2019.05a
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• pp.107-108
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• 2019

The interlayer noise of the apartment house is a typical problem that reduces the quality of the residential environment. Therefore, many researchers have developed soundproofing materials that blocks noise between floors. However, most development technologies do not have the noise cut-off effect felt by residents, and may also have a defect in long-term deflection. In this respect, this study developed high-performance interlayer soundproofing material that can overcome existing problems. The developed technology has the noise reduction effect experienced by the residents and it has high durability without long-term deflection. Therefore, high-performance interlayer soundproofing material is expected to contribute to reducing disputes over noise between floors of apartment residents.

• Proceedings of the Korea Concrete Institute Conference
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• 2010.05a
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• pp.457-458
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• 2010

PHDC(Promoted High Durability Concrete) is developed for preventing the chlroide attack to concrete structure on the reclaimed ground. In this study, the basic characteristics and the field application of PHDC is examined through experiments, the durability standard of the company is suggested. the long-term monitoring experiment for measuring the chloride penetration is also performed.

• Proceedings of the Korea Concrete Institute Conference
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• 1995.10a
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• pp.80-83
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• 1995

In order to develope and apply high-performance steel fiber reinforced concrete (SFRC), the effects of steel fibers on durability and long-term deformation of SFRC due to various mixing conditions have been studied. As the test result show, the manufacturing process technology of industrial SFRC is developed And the durability of SFRC such as freeze-thaw, resisteance abrasion resistance are significantly improved, the drying shrinkage of SFRC, is remarkably decreased by increasing the steel fiber contents than plain concrete

• Proceedings of the Korean Institute of Building Construction Conference
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• 2022.04a
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• pp.107-108
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• 2022

This study aims to solve environmental problems by reducing complex degradation and recycling industrial waste by utilizing waste fibers and blast furnace slags, which are industrial by-products. In addition, it is intended to secure long-term durability to reduce cracks. To this end, the disadvantages of fiber-reinforced concrete are to solve the problem of lowering liquidity and ensuring curing time, and to find the optimal combination when waste fibers and blast furnace slag are used together.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.05a
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• pp.101-102
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• 2023

This study aims to mix the base concrete by mixing latex to improve the durability performance to reduce the composite deterioration of the base concrete. Latex fiber has high resistance to freezing and thawing, adhesion, and deicing agent (calcium chloride), and it is used to secure long-term durability to reduce cracking and compound deterioration of concrete. In addition, through experiments, we are trying to find ways to improve the strength of concrete by studying the mixing of the appropriate mixing ratio of latex.

• Journal of the Korean Recycled Construction Resources Institute
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• v.4 no.2
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• pp.149-156
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• 2016

It has been well known that concrete structures exposed to chloride and sulfate attack environments lead to significant deterioration in their durability due to chloride ion and sulfate ion attack. The purpose of this experimental research is to evaluate the long-term durability against chloride ion and sulfate attack of the alkali activated cementless concrete replacing the cement with ground granulated blast furnace slag. For this purpose, the cementless concrete specimens were made for water-binder ratios of 40%, 45%, and 50%, respectively and then this specimens were cured in the water of $20{\pm}3^{\circ}C$ and immersed in fresh water, 10% sodium sulfate solution for 28, 91, 182, and 365 days, respectively. To evaluate the long-term durability to chloride ion and sulfate attack for the cementless concrete specimens, the diffusion coefficient for chloride ion and compressive strength ratio, mass change ratio, and length change ratio were measured according to the NT BUILD 492 and JSTM C 7401, respectively. It was observed from the test results that the resistance against chloride ion and sulfate attack of the cemetntless concrete were comparatively largely increased than those of OPC concrete irrespective of water-binder ratio.