• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.789-792
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• 2005

Development of high-strength concrete and improved durability has brought new opportunities to the construction industry. However, some attention was given to characteristics of such concrete, in particular with respect to their cracking sensitivity. It has been argued and demonstrated experimentally that a low water/cement ratio concrete undergoes shrinkage due to self-desiccation. This so-called autogenous shrinkage cracking is a major concern for concrete durability. One possible method to reduce cracking due to autogenous shrinkage is the addition of expansive additive. Tests conducted by many researches have shown the beneficial effects of addition of expansive for reducing the risk of shrinkage-introduced cracking. This paper aimed at forecasting deformation of high strength cement paste with expansive additive for early age.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.461-464
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• 2003

Portland Cement Concrete (PCC) pavements have the advantage of durability and superior surface friction when compared to most dense-graded asphalt. However, data collected to date generally show PCC pavements to create more noise than asphaltic surfaces. As the results of research, surfaces of exposed aggregate, tining and grooving concrete pavements appear to provide better noise quality characteristics as well as good frictional characteristics and durability. In this paper, several methods of texturing were considered to reduce tire/pavement noise. As the results of this paper, PCC pavements with special texturing have superior surface friction as well as noise reductions when compared to conventional PCC pavement. Especially, Exposed Aggregate Concrete (EAC) surface appears to provide better noise quality characteristics. Conclusively, if overall noise and safety are considered simultaneously, EAC pavement that provides satisfactory friction as well as better noise reductions is suggested.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2016.10a
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• pp.41-42
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• 2016

As the importance of maintenance of reinforced concrete structure recently has emerged, the attention of durability of structure has been increasing. There are many studies about durability decline especially due to the carbonation. In order to study carbonation progress after surface repair of carbonated concrete, each carbonation penetration velocity from different repair materials of concrete structure is compared through the experiment of carbonation accelerating CO₂ concentration to 20% and 100%. As carbonation infiltration progress is predicted through this study, the counterplan of service life evaluation will be prepared on selection of repair materials of concrete structure.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2019.05a
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• pp.30-31
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• 2019

Carbonation of the root concrete reduces the durability of the reinforced concrete, and it is important to check the carbonation resistance of the concrete to ensure the durability of the reinforced concrete structure. In this study, a basic study on the prediction of carbonation progress was conducted by considering the mixing conditions of concrete using deep learning algorithm during the theory of artificial neural network theory. The data used in the experiment used values that converted the carbonation velocity coefficient obtained from the mixing conditions of concrete and the accelerated carbonation experiment into the actual environment. The analysis shows that the error rate of the deep learning model according to the Hidden Layer is the best for the model using five layers, and based on the five Hidden layers, we want to verify the predicted performance of the carbonation speed coefficient of the carbonation test specimen in which the exposure experiment took place in the real environment.

• Advances in concrete construction
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• v.6 no.5
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• pp.527-543
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• 2018

Crack control of precast members is crucial for durability. However, there is no clear provision to check the crack width of precast joints. This study presents an experimental investigation of loop joint details for use in a precast bridge deck system. High strength concrete of 130 MPa was chosen for durability and closer joint spacing. Static tests were conducted to investigate the cracking and ultimate behavior of test specimens. The experimental results indicate that current design codes provide reasonable estimation of the flexural strength and cracking load of precast elements with loop joint of high strength concrete. However, the crack width control of the loop joints with high strength concrete by the current design practices was not appropriate. Some recommendations to improve crack control of the loop joint were derived.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.597-600
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• 2006

In this study, field survey of carbonation for RC column in city is carried out and carbonation behavior in sound, joint, and cracked concrete is also analyzed. Futhermore, probability of durability failure with time is calculated through considering probability variables such as concrete cover depth and carbonation depth which are obtained from field survey. The probability of durability failure in cracked concrete with considering crack width and time is also calculated and service life is predicted based on intended failure probability in domestic specification. Through this study, it is known that service life in a RC column is evaluated differently for local conditions and each service life is rapidly decreased with decrease in cover depth and increase in crack width.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.885-888
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• 2006

Nowaday, High strength concrete(HSC) has been mainly used in high rise building. HSC have superior property as well as improvement in durability compared with ordinary strength concrete. In spite of durability of HSC, explosive spalling in concrete front surface near the source of fire occurs serious problem in structural safety. Thus, this study is concerned with experimentally investigation fire resistance of the inorganic fire protection materials at high temperatures up to $800^{\circ}C$. From the test result, developed inorganic binder becomes general that with rising temperature the compressive strength of the material increases in tendency. Therefore, the results indicate that it is possible to fireproof panels, fire protection of materials, etc.

• Journal of the Korea institute for structural maintenance and inspection
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• v.6 no.1
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• pp.205-212
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• 2002

The deterioration rate of concrete structures in urban area is accelerated due to rapid urbanization and environmental pollution. Repair materials and methods newly introduced in Korea should be investigated whether they are appropriate for the urban environment in Korea. The creek concrete structures are exposed in severe environmental condition than others. Based on these background in mind, the study is focused on evaluation of performance on repair materials used to rehabilitate creek concrete structures. To evaluate the performance of repair materials, four kinds of repair materials were selected based on polymer emulsion. This experimental study was conducted on fundamental performance such as setting time, compressive strength, bending strength, bonding strength, thermal expansion coefficient, and durability performance such as chloride diffusion, carbonation, chemical attack, and steel corrosion rate. On the basis of this study, the optimal repair material which is proper to the environment condition can be selected and service life of creek concrete structures can be extended. As a result, the life cycle cost can be reduced and the waste of material resources will be cut down.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.11a
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• pp.59-60
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• 2021

The unit-water content has a major problem in concrete structures which leads to micro cracks on the concrete during drying time. Thus, the compressive strength and durability of the concrete structures are significantly reduced. Several techniques have been developed to measure the unit-water content in concrete structures such as heating drying, unit volume mass, and capacitance measurements. However, these techniques have problems in during measurement such as longer time, expensive and difficult in analysis of data. Frequency Domain Reflectivity (FDR) is one of the sensors which used to measure the water content. This method has several advantages including easy to measure, inexpensive, and capable of measuring moisture in real time. In this study, an attempt has been made to evaluate the unit-water content in concrete using the FDR sensor and interpret the data with deep learning method.

• Journal of the Korea Concrete Institute
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• v.18 no.2 s.92
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• pp.249-255
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• 2006

Recently, interest grew on the quality of aggregates following the diminution of primary resources from river as to grow construction demand and the low grade of nature sand like sea sand. following, need is to diversify the supply sources of fine aggregates which are excessively relying on sea sand and urgency is to find as soon as possible aggregate resources that can substitute sea sand. On the other hand, various fine aggregates we utilized to produce concrete in the domestic construction fields. However, few studies have been systematically investigated on the effects of such fine aggregates on concrete properties. Therefore, this study examined the effects of comparatively widely used fine aggregates in the domestic construction fields on the shrinkage, durability and watertightness of concrete. Results revealed that drying shrinkage increases, and durability and watertightness degrades for concrete using crushed sand than natural fine aggregates like sea sand and river sand. Especially, the use of crushed sand exhibiting bad grain shape and grade was larger adverse effect on the quality of concrete. In addition, appropriate adjustment of the grain shape and grade during the blending of crushed sand exhibiting bad grain shape and grade with natural aggregates appeared to enhance the shrinkage and durability of concrete.