• Computers and Concrete
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• v.14 no.6
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• pp.727-743
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• 2014

The management of existing concrete bridges has become a major social concern in many developed countries due to the large number of bridges exhibiting signs of significant deterioration. This problem has increased the demand for effective maintenance and renewal planning. In order to implement an appropriate management procedure for a structure, a wide array of corrective strategies must be evaluated with respect to not only the condition state of each defect but also safety, economy and sustainability. This paper describes a new performance evaluation system for existing concrete bridges. The system evaluates performance based on load carrying capability and durability from the results of a visual inspection and specification data, and describes the necessity of maintenance. It categorizes all girders and slabs as either unsafe, severe deterioration, moderate deterioration, mild deterioration, or safe. The technique employs an expert system with an appropriate knowledge base in the evaluation. A characteristic feature of the system is the use of neural networks to evaluate the performance and facilitate refinement of the knowledge base. The neural network proposed in the present study has the capability to prevent an inference process and knowledge base from becoming a black box. It is very important that the system is capable of detailing how the performance is calculated since the road network represents a huge investment. The effectiveness of the neural network and machine learning method is verified by comparing diagnostic results by bridge experts.

• Journal of The Korean Digital Architecture Interior Association
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• v.13 no.4
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• pp.61-68
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• 2013

Concrete structure is not the only material vulnerable to physical and chemical processes of deterioration associates with severe conditions. Deterioration of the concrete structure, however, occurs more progressively from the outside of the concrete exposed to severe conditions. Especially, Carbonation, chloride ion attack is more important factor of concrete durability. This study is interested in manufacturing the self-cleaning concrete surface impregnant including TEOS, lithium silicate for the repair of the exposed concrete surface and the color concrete requiring the advanced function in view of the concrete appearance. Form the results, TEOS and lithium silicate are very effective that increasing the concrete durability using self-cleaning concrete impregnant. Self-cleaning concrete impregnant specimens is satisfied with performance requirement of KS standard in adhesion test in tension but the reinforcement of concrete substrate is slight. So, the self-cleaning concrete impregnant of this study is more desirable for the improvement of durability rather than the reinforcement.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.1549-1554
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• 2008

In this paper, The evaluation of durability of the PC Panel lining for tunnel structure was examined through the rapid test by carbonation and freezing and thawing. Also for the purpose of improvement of durability. Namely, the durable characteristics of PC Panel lining by carbonation and freezing and thawing, was evaluated by rapid test and long-term field exposure test and main influence factors were derived. As a result of test, Correlation of accelerating test in deterioration chamber and long-term field exposure test, it will be expected that the proposed correlation well to the prediction of life expectancy of structure and is contributed greatly in the future.

• Journal of the Society of Disaster Information
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• v.13 no.3
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• pp.332-339
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• 2017

In the case of aged structures, the information of the structure is often lost after the completion of construction, and there is a great difficulty in predicting the durability life of the structure due to the lack of information on concrete formulations. In this study, the durability of concrete specimens was evaluated by various field and indoor test methods based on the core specimens collected from the field, and the durability life of the concrete structures was predicted by using the FEM analysis technique.As a result, the neutralization rate coefficient was $5.38E-6(cm^2/day)$ and the rate of progress was low. And the possibility of complex deterioration due to carbonation and salting was found to be very low.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.795-798
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• 1999

Deterioration induced by the freezing and thawing in concrete often leads to the reduction in concrete durability by the cracking or surface spalling. In this paper, the deterioration prediction model for concrete structures subjected to the irregular freeze-thaw was proposed from the results of accelerated laboratory test using the constant temperature condition and acceleration factor from the in-situ weather data.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.651-656
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• 2003

Durability of concrete is possibly related to externally-induced chemical attacks in addition to internally-induced deterioration. Externally-induced chemical attacks can be derived from various sources according to environmental conditions under which concrete structures are existing. The present study investigates the characteristic concrete deterioration and formation of secondary minerals by external chemical attacks under certain environmental condition. Petrographic microscope, SEM, EDAX, XRD analyses were conducted to identify secondary mineral formation and micro-structural analyses.

• Proceedings of the Korea Concrete Institute Conference
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• 1996.10a
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• pp.169-174
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• 1996

It have been announced that concrete subjected to freezing and thawing cause deterioration by expanded inside water and contracted at thawing. However, this study descrebe the deterioration mechanism of concrete by freezing and thawing test. Embeded strain gauges were used to measure the inside restrict strain due to the temperature differenct inside and outside the concrete test specimens. Test results showed that using the air entrained admixture and expanded poly-styrene was developed durability of concrete by decreasing inside retrict strain ratio.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.676-681
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• 2000

This paper covers durability and field application of marine concrete which have been enhanced the resistance against deterioration in seawater. Fly ash concrete is applied to make the concrete with good durability. It is well known fly ash in concrete has a good performance preventing fro a sulphate attack and a steel corrosion. Several durability tests were performed to find characteristics of marine concrete which is proposed in this paper comparing with normal concrete. Field application was executed to compare results with laboratory test and to give a reliability to engineers. The project was supported by Ministry of Marine Affairs and Fisheries for two years.

• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.1
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• pp.123-130
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• 2006

The duties of the restorative materials are to bear up against stress and to protect reinforcement corrosion. So the restorative materials are estimated by various kinds of strength, permeability and etc, But, in case of existing performance evaluation of restorative materials, because various deterioration factors are separately acted, the system of performance evaluation is different from that of combined deterioration of real structure and it is difficult to evaluate the exact performance of restorative materials. In this study, to evaluate Performance of restorative materials, we compare their korea standard properties in terms of compressive and bending strength and permeability of water and air with real durability for carbonation, salt damage and actual reinforcement corrosion like ratio of corrosion area. weight reduction and corrosion velocity of steel bar under environment of combined deterioration. The results showed that strength and permeability of restorative materials are similar but their resistance to carbonation, salt damage and actual reinforcement corrosion are very different.

• The Journal of Engineering Geology
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• v.23 no.4
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• pp.341-352
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• 2013

The physical and mechanical properties of red shale and black shale exposed in the Daegu area were investigated in tests conducted to determine unit weight, absorption ratio, porosity, ultrasonic velocity, unconfined compressive strength, point load strength, slake durability index, and deterioration characteristics. XRD, XRF, and SEM analyses were also performed on the shale specimens. While the unit weights of the two shales were similar, the absorption ratio and porosity were higher in the red shale than in the black shale. Despite the higher porosity of the red shale, the ultrasonic velocity, compressive strength, and point load strength were higher in the red shale, which is an unexpected result that may be due to the presence of fine laminations in the black shale. The deterioration rate, as determined from the point load strength and the slake durability index, increased with increasing immersion time and with the acidity of the immersion liquid. The deterioration rate was higher for the red shale than for the black shale because of the higher porosity of the former.