• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.633-636
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• 2008

In order to efficient use of land and development of human, a lot of research on the utilization of underground space is being progress. For the smooth flow of traffic, in the case of mountainous terrain like our country, construction of the tunnel is rapidly increasing. The NATM method is used mainly in the domestic. And also, a lot of research for the NATM is underway, but aspects of the material are lacking. In this study, therefore, it is to evaluate the properties of durability according to mixing ratio and a kind of mineral admixture for the development of shotcrete performance by using the MATM.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.6
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• pp.249-256
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• 2008

The durability of marine concrete structure is severely degraded by corrosion due to penetration and diffusion of chloride. So, many researches have been performed to improve the durability in marine concrete structure. In this study, the concrete members mixed with the mineral admixtures(SF and BFS), the epoxy-coated steel, and corrosion inhibitors are prepared, and four-point bending test of specimens are performed to investigate the flexural behaviors and the applicability for marine concrete structure. From the test results, the mineral admixtures and inhibitors are useful for safety against the initial cracking and the bending resistance in specimens. When the durable material is used in specimen, the tensile stress of reinforcing rod was less variable in same bending span length, and the durable member showed a stable behavior. And it is evaluated that the crack spacing is not larger in specimen used the durable material.

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.1
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• pp.159-168
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• 2011

In this study, we find out the feasibility of self-consolidating concrete with EP nylon fiber. Three kinds of method were used; when length of nylon fiber is differed for the experiment to investigate usability of nylon fiber with enhanced performance by dispersing-agent coating in self-consolidating concrete, when mixing in other organic fibers (polypropylene, cellulose) and in case of Binary Blended and Ternary Blended concrete mixed with different types of mineral admixtures (blast-furnace slag and fly ash). Based on the results of the experiment described above, comparison was made on the basic properties and dynamic characteristics of general fiber reinforced concrete mixed with enhanced performance nylon fiber and SCC mixed with enhanced performance nylon fiber as a Mock-up test prior to the experiment of application to the actual structure. Considering characteristics and durability of the fresh and hardened self-compacting concrete, dynamic characteristics and durability were found to be more outstanding when using nylon fiber for the mineral admixtures used, dynamic characteristics and durability were found to be more outstanding when using blast-furnace slag.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.4A
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• pp.347-353
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• 2009

The qualitative factors influencing the ingress of chloride ion into concrete are water-binder (W/B) ratio, cement type, age, chloride ion concentration of given environment, wet and dry conditions, etc. Thus, an objective of this experimental research is to investigate the effects of cement types and environmental conditions on the chloride ion diffusion characteristics in concrete through the chloride ion diffusion test. For this purpose, the diffusion coefficients for chloride ion in concrete with three types of cement such as ordinary portland cement (OPC), binary blended cement (BBC), and ternary blended cement (TBC), were measured for the concrete specimens with W/B ratios of 32%, 38%, and 43%, respectively. The diffusion coefficients for chloride ion were also measured for the concrete specimens with W/B ratio of 43%, which were subjected to standard curing and field exposure conditions. It was observed from the test results that the resistance against chloride ion penetration increased with decreasing W/B ratio and those of BBC and TBC concretes were greater than that of OPC concrete. Therefore, it was revealed that the use of these cements containing mineral admixtures is required to extend the service life of RC structures exposed to chloride environment. On the other hand, it was noted that the resistance against chloride ion penetration of field exposure test specimens was slightly lower than that of standard curing test specimens due to the penetration of chloride ion under the irregular ambient temperature, splash of wave, and cycle of wet and dry.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.04a
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• pp.335-340
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• 1997

The mineral admixtures, ground granulated blast furnace slag (GSB) and fly ash (FA), were mixed with ordinary portland cement(OPC) in order to reduce temperature rise and slump loss in concrete. In according to concrete replaced with 30% of GBS, the compressive strength of that developed to 574 kg/$\textrm{cm}^2$ at age of 28days and maximum temperature decreased to the extent of $5^{\cire}C$. When GBS and FA are mixed with concrete, it can be estimated that mix proportions of them have to be taken into consideration.

• Journal of the Korea Concrete Institute
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• v.23 no.3
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• pp.339-346
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• 2011

The effects of mineral admixtures on the bonding properties of cement mortar to polyolefin based synthetic fiber were evaluated. The mineral admixtures consisted of 0%, 5%, 10%, and 15% fly ash, blast furnace slag, and metakaolin in cement. Bond interactions between the cement mortar and the polyolefin based synthetic fiber were determined by Dog-bone bond tests. Bond tests of the polyolefin based synthetic fiber showed an increase in pullout load with the strength of the cement mortar. Also, the interface toughness of polyolefin based synthetic fiber in cement mortar increased as the fly ash, blast furnace slag, and metakaolin contents increased. The microstructure of polyolefin based synthetic fiber surface was examined after the pullout test to analyze the frictional resistant force according to the replacement ratio of fly ash, blast furnace slag, and metakaolin during the pullout process of polyolefin based synthetic fiber in cement mortar. The scratched of polyolefin based synthetic fibers increased with the replacement ratio of fly ash, blast furnace slag, and metakaolin. Also, the interface toughness was enhanced by adhesion forces induced by the fly ash, blast furnace slag, and metakaolin.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.741-744
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• 2008

There are two ways to reduce cement content for a given quality level(strength, workability etc.) in concrete. First, reducing the required paste volume by varying the shape or the grading of aggregates. Secondly, holding the paste volume constant while replacing cement volume with mineral admixtures or mineral fillers. And It will also be proved that the required minimum paste volume is independent of the paste composition, provided the paste composition is in a reasonable range. In this study, therefore, we have an object to determine the required minimum paste volume for a given workability level. For this purpose, we tried the following experiments: vary the paste volume for the three different grading of aggregates and determine the minimum paste volume to achieve a certain level of workability with high-range water reducing admixture.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.2
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• pp.75-81
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• 2010

In this study, when concrete properties are changed by concrete mix proportions or blending of admixtures, the characteristics of electro-chemical method for corrosion assessment of the embedded steel are compared and its causes are analyzed. According to the results, when the ratio of corroding area was less than 10%, the half-cell method was affected by concrete properties. In the case of specimen blended admixtures, it is possible to assess the high-corroded steel qualitatively using the half-cell method. For the polarization resistance method, though the corroding area was less than 10%, it has not affected by concrete properties. However, in case of specimen blended admixtures, the corrosion level of steel was underestimated than OPC specimens having a similar corroding area.

• Proceedings of the Korea Concrete Institute Conference
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• 2010.05a
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• pp.341-342
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• 2010

This paper presents rheology of mortar using mineral admixture(Ground granulated blast furnace slag and Fly ash). The measurement of the rheology of mortar, including viscosity and yield stress, as well as its compressive strength were also carried our.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.19 no.4
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• pp.320-328
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• 2007

The durability of marine concrete structures is severely degraded by corrosion due to seawater attack and diffusion of chloride in concrete. The deduction of durability causes high repair cost for maintenance of marine concrete structure. So, the applicability of high-durable materials is investigated to improve the durability in marine concrete structures. For these, the characteristics of corrosion prevention of marine concrete structures mixed with the mineral admixtures(SF, FA and BFS), the modified steel(stainless and coating steel), and corrosion inhibitors are evaluated using electro-chemical methods. As a results of this study, it is quantified for the effect of promotion of durability by high-durability materials in marine concrete structures.