• Proceedings of the Korea Concrete Institute Conference
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• 2005.05b
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• pp.441-444
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• 2005

Our country has experienced variations in temperature as belong to the area of the continental climate that shows four significant seasons. These occur immense difficulty on the period, cost, quality of construction. As the hydration of cement processes, the strength of concrete is developed. In order to improve the quality of concrete, various conditions including temperature and humidity should be maintained appropriately and concrete itself should be cured sufficiently. In the early age, the strength of concrete is developed remarkably. However, the hydration is accelerated too much in high temperature or delayed too much in low temperature, so the quality can be changed and It can fail to get the objective strength. This paper aims to offer the data, necessary to the quality control handbook.

• Proceedings of the Korea Concrete Institute Conference
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• 1992.04a
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• pp.7-12
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• 1992

The aim of this study is to develop economical High-Strength and High-Quality Concrete, and to assure quality control of Concrete in the field. For this purpose, Five types of Mixing Methods are examined and the relationship between slump loss and slump recovery by transport is studied. As a result, workability and strength are dependent on the Mixing Method, although the Mixing proportions are same, Also, adding admixture in the field is proposed as an alternative to consider the relationship between slump loss and slump recovery.

• Advances in concrete construction
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• v.1 no.1
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• pp.45-63
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• 2013

Upon completion of new concrete structures, the achieved construction quality always shows a high scatter and variability, and in severe environments, any weaknesses and deficiencies will soon be revealed whatever durability specifications and materials have been applied. To a certain extent, a probability approach to the durability design can take the high scatter and variability into account. However, numerical solutions alone are not sufficient to ensure the durability and service life of concrete structures in severe environments. In the present paper, the basis for a probability-based durability design is briefly outlined and discussed. As a result, some performance-based durability requirements are specified which are used for quality control and quality assurance during concrete construction. The final documentation of achieved construction quality and compliance with the specified durability are key to any rational approach to more controlled and increased durability. As part of the durability design, a service manual for future condition assessment and preventive maintenance of the structure is also produced. It is such a service manual which helps provide the ultimate basis for achieving a more controlled durability and service life of the given concrete structure in the given environment.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.10a
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• pp.239-242
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• 2002

This study is intended to investigate the relationship between rebound value of P type schmidt hammer and the compressive strength with various aggregates, and a series of experiments about early strength quality control by P type schmidt hammer was performed. According to the results, the compressive strength of concrete using basalt and limestone aggregate is higher by 3% and lower by 4% than that of concrete using granite aggregate respectively. Concrete using basalt and lime stone aggregate show high rebound value in vertical strike. Estimation of the compressive strength does not show differences in horizontal strike, but the compressive strength is estimated high in order of granite, basalt and limestone aggregate in vertical strike. A good correlation between the rebound value of schmidt hammer and the compressive strength is confirmed regardless of aggregate types, so it could be possible to control the quality of concrete by P type schmidt hammer test when basalt and limestone aggregates are used at the same time.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.245-248
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• 2004

The prediction of the strength of cold weather concrete and the analysis of the insulating material effect were performed to apply the prediction function with maturity concept for quality control of them in this study. The several results driven from above processes were summarized as followings. First, the difference between the temperature of cylinder covered with insulating materials and that of cylinder without them was $4.5\~6.0^{\circ}C$. Second, the maturity of concrete was suggested to be keep higher than $96\~115^{\circ}C{\cdot}D$ until at least 7-day and the temperature of fresh concrete was suggested to be keep above $10^{\circ}C$ directly after set.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.10a
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• pp.380-385
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• 1998

Nowadays, shotcrete plays an essential part in he construction of underground structures, and steel fiber is so useful for increasing the toughness of the concrete that is spotlighted at tunnel or pavement site. A variety of tests have been developed to measure and quantity the improvements achievable in steel fiber reinforced concrete(SFRC) and shotcrete. But Korea doesn`t have specific standards in this respect, and the only criteria that KHC(Korea Highway Corporation) applies to tunnel shotcreting are flexural strength and toughness quotient. Test results in order to manage the quality of steel fiber reinforced concrete and shocrete are very affected by various test method. Therefore, this study deals with the test methodological effects on SFRC quality. The major interests are loading method, that is, load control and displacement control, loading velocity, support condition.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.04a
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• pp.287-292
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• 1999

Mass concreting in cold weather environment should be focused on the control of thermal crack caused by high hydration heat rather than curing method for protecting from frost damage at early age because the thermal stress have much influence on the quality of structure placed in cold weather. Therefore, in this paper, the control of thermal crack of mass concrete in cold weather environment are dealt with preparing the practice plan for mass concrete and placing the concrete according to the plactice plan. According to the results, we can obtain good quality mass concrete without thermal crack caused by the difference of temperature between inner part and outer part.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.105-108
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• 2006

Recently, trouble of sand supplying is occurred according to exhaustion of natural sand resources. Therefore various measures are proposed for solution of trouble of sand supply and crushed sand among measures is used as one of most universal measures. But because crushed sand have poor particle shape and plenty of mikes micro particle, the quality of concrete using crushed sand deteriorated. Therefore, this study evaluated engineering property of concrete with replacement ratio of crushed sand and EEZ sand applied evaluation result to fundamental data for quality control of concrete using crushed sand and EEZ sand and The result of this study have shown that quality of concrete using crushed sand and EEZ sand and The compressive strengh of concrete up to 50, 70% EEZ sand replacement by crush sand, nearly equal to that of general sand.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.04a
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• pp.9-14
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• 1998

In this paper, we described the basic elements(flowabiligy, fillingability, elapsed time, pumpability, no-vibrating effects, and etc.) required for the application and quality control of the super flowing concrete(SFC) in Top Down site. Also, manufactured sand and fly ash were used for investigating characteristics of SFC through various experiments(mix design, optimum mix condition) before placing the concrete in site. As a result of this project, the developed SFC shown high flowability and self-fillingability in the joint good enough for the requirement. Futhermore, inner uniformity of the no-vibrated concrete was verified by testing reformed space. Therefore, quality control and compressive strength(360kg/$\textrm{cm}^2$) can be secured by using SFC even without vibrating.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.297-302
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• 2001

SRC pier at KTE 6-1 construction area is a very important structure. Precise control of quality is needed. This pier has 3.50m$\times$3.73m section and 38.20m length. So this structure must be treated as mass concrete and thermal crack caused by hydration heat should be controled. In this project belite cement concrete is used to control the thermal crack. As a result of adapting belite cement concrete perfect control is achieved. Finally, hydration heat FEM analysis of horizontal element is executed for Ordinary Portland Cement concrete and belite cement concrete. In comparison of two results, it is confirmed that using low heat portland cement concrete is necessary.