• Proceedings of the KSR Conference
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• 2006.11b
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• pp.1385-1390
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• 2006

Concrete structure can be deteriorated by ingress of moisture and aggressive agents. To maintain the sound performance of concrete structure during the service life, it needs to protect concrete from ingress of moisture and aggressive agents before arising deterioration of concrete. Protection of concrete is possible by surface treatment. In this study, durability of the functional nano composite inorganic activated carbon based coatings which can provide a barrier against the ingress of moisture or aggressive ions to concrete is discussed. For the durability evaluation of the coatings, fine void structure evaluation test, chloride penetration acceleration test, accelerated carbonation test, freezing and thawing test, and the accelerated test of chemical erosion are conducted. As the result of this study, the functional nano composite inorganic activated carbon based coatings which became one formed complex compound with adsorption and porosity on concrete surface, had an effect on the function of far infrared radiation, antimicrobial action, air cleaning, airing assurance, and the interception of moisture of deterioration factor, chloride ion, carbon dioxide, sulfate, and so on.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.6
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• pp.197-205
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• 2020

In 2014, The Housing Act amended to allows vertical extension and increases the units of housing (or total floor area) to site. Currently, the feasibility of performing vertical extension is evaluated based on safety diagnosis provisions and manuals with 1st investigation stage on slope, uneven settlement, load-bearing capacity, and durability. However, a need for more reasonable evaluation criteria for the investigation is still required because there had not been any other case study on the diagnosis for the vertical extension, and the engineering basis on evaluation criteria were not suggested. Accordingly, this study is intended to suggest feasible evaluation criteria on the carbonation, chloride ion contents, corrosion of reinforcements, crack and surface deterioration of concrete for durability assessment by codes and standards of domestic and foreign countries. The results of this study are expected to be beneficial for establishing more reasonable durability evaluation criteria, and in turn, more reliable assessment protocol for vertical extension.

• Journal of Korean Tunnelling and Underground Space Association
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• v.9 no.3
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• pp.299-307
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• 2007

In this study, a new concept for simulating a physical damage of tunnel shotcrete lining due to a long-term chemical deterioration has been proposed. It is known that the damage takes place mainly by internal cracks, reduction of stiffness and strength, which results mainly from volume expansion of the lining and corrosion of cement materials, respectively. This damage mechanism of shotcrete lining appears similar in most kinds of chemical reactions in tunnels. Therefore, the mechanical deterioration mechanism induced by a series of chemical reactions was generalized in this study and mathematically formulated in the framework of thermodynamics. The numerical model was implemented to a 3D finite element code, which can be used to simulate behaviour of tunnel structures undergoing external loads as well as chemical deterioration in time. A number of illustrative examples were given to show a feasibility of the model in tunnel designs.

• Journal of the Korean Society for Railway
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• v.9 no.4 s.35
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• pp.349-356
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• 2006

At present, the selecting system and analytic estimation criterion on repair materials and methods of the deteriorated RC structures have not yet been set up in domestic. Under these circumstances, deterioration such as shrinkage crack, corrosion of rebar has been often occurred after repair, and this finally results in too frequent repairs. In this study, three types of repair methods were experimentally investigated by the accelerating test in a combined deterioration chamber and long-term field exposure test. Three types of repair methods applied in this study belong to a group of polymer cement mortar, which is commonly used in repair works. According to the results of this study, durability of repair mortar layers and corrosion properties of recovered rebar could be investigated in short period by the accelerating test in a combined deterioration chamber, which can simulate the condition of repeated high-and-low temperature and repeated dry-and-wet environment, spraying chloride solution and emitting $CO_2$ gas. After 36 month long-term filed exposure test in the coastal area, harmful macro-cracks are observed in the polymer cement mortar layer of some repair methods. These crack are considered to result from drying shrinkage of polymer cement mortar. Also, after 36 month exposure, amount of corrosion area and weight loss of rebar are found to be different according to the types of repair methods.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.2
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• pp.1096-1101
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• 2014

This study (II) has appled the new assessment model of large-diameter pipe deterioration proposed by the study (I) to the metropolitan multi-regional water supply system (1st phase). In the total 30 pipelines, 24 and 27 pipelines were required for improvement as results from the existing evaluation methods 1995 and 2002, respectively. The assessment results were almost similar in the new developed model and the existing methods. It is founded that the new simple model developed in this study can produce reliable results, consistent with those from the existing methods requiring many factors for a pipe deterioration assessment. It is therefore expected that the new model would be helpful in practical applications of a pipe deterioration assessment since it can save both temporal and economic costs for experiments and analysis, as compared with existing assessment methods.

• Journal of the Korea Concrete Institute
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• v.19 no.1
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• pp.47-56
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• 2007

Recently, tunnels are increasingly constructed in this country with the increased construction of highways, high-speed railways and subways. Shotcrete is one of the major processes in the tunnel construction. Many problems, however, exist in the current shotcrete practice. The purpose of the study is, therefore, to explore the trobles in the current shotcreting practice, and to develop high-quality silica fume shotcrete. For the purpose of security a long-term durability of shotcrete, this study conducted combined deterioration tests. In this study, a combined deterioration test in consideration of a variety of deterioration factors were proceeded. Especially, micro-silica fume that was used frequently in overseas because of a outstanding strength-promotion effect was applied to combined deterioration test, and a long-term durability of shotcrete was investigated according to additions mixing. As a result of test, the shotcrete mixed Micro-silica fume showed a good deterioration quality compared with the other mixes. And is shows that the Micro-silica fume has an outstanding strength-promotion effect and is effective to secure a long-term durability of shotcrete by means of decreasing a deterioration caused by steel fiber mixed.

• Journal of the Korea institute for structural maintenance and inspection
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• v.1 no.1
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• pp.53-64
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• 1997

Recently, safety evaluation of structures has received great concern in this country. One major problem in safety evaluation is that the results are often quite different depending upon evaluation authority. This is mainly due to arbitrary selection of various modification factors when employing allowable stress method for safety evaluation, The purpose of the present study is, therefore, to establish a rational method to determine the modification factors, especially the stress modification factor and the deterioration modification factor based on visual examination. It is thought that the proposed method yields a rational and consistent result for safety evaluation and may efficiently be used for realistic evaluation of load capacity of bridge structures.

• Journal of Korean Neurosurgical Society
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• v.63 no.3
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• pp.358-365
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• 2020

To describe how to perform urological evaluation in children with tethered cord syndrome (TCS). Although a common manifestation of TCS is the development of neurogenic bladder in developing children, neurosurgeons often face difficulty in detecting urological problems in patients with TCS. From a urological perspective, diagnosis of TCS in developing children is further complicated due to the differentiation between neurogenic bladder dysfunctions and transient bladder dysfunctions owing to developmental problems. Due to the paucity of evidence regarding evaluation prior to and after untethering, I have shown the purpose and tools for evaluation in my own practice. This may be tailored to the types of neurogenic bladder, developmental status, and risks for deterioration. While the urodynamic study (UDS) is the gold standard test for understanding bladder function, it is not a panacea in revealing the nature of bladder dysfunction. In addition, clinicians should consider the influence of developmental processes on bladder function. Before untethering, UDS should reveal synergic urethral movement, which indicates an intact sacral reflex and lack of TCS. Postoperatively, the measurement of post-void residual urine volume is a key factor for the evaluation of spontaneous voiders. In case of elevation, fecal impaction, which is common in spinal dysraphism, should be addressed. In patients with clean intermittent catheterization, the frequency-volume chart should be monitored to assess the storage function of the bladder. Toilet training is an important sign of maturation, and its achievement should be monitored. Signs of bladder deterioration should be acknowledged, and follow-up schedule should be tailored to prevent upper urinary tract damage and also to determine an adequate timing for intervention. Neurosurgeons should be aware of urological problems related to TCS as well as urologists. Cooperation and regular discussion between the two disciplines could enhance the quality of patient care. Accumulation of experience will improve follow-up strategies.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.04a
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• pp.813-818
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• 1999

The construction of large scale civil and building structures which form the base of social economy has been grown greatly. As the increasing of aged and deteriorated structures, it is necessary to evaluate the safety of those structures. The deterioration, safety evaluation, repair and rehabilitation are important problems in the construction area that every country faces. This paper presents the general information on how to conduct a data analysis of long-term monitoring system and evaluate the characteristics of surveying methods.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.1061-1066
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• 2003

Chloride penetration into concrete is the main cause of the steel corrosion in concrete structures exposed to chloride-rich environments. Protective surface coatings are increasingly being applied to concrete structures to reduce chloride penetration. In this study, the performance of various surface coatings was evaluated. Most coatings showed good results for the various tests of the performance evaluation. Surface coatings can delay deterioration such as chloride-induced reinforcing bar corrosion effectively.