• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.357-360
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• 2006

Under sustained load, the stress variation occurs due to creep and shrinkage of concrete on the sections of steel-concrete composite girders. In standard specification for highway bridge, the method of stress estimation considering time effects is based on the concept of Yassumi method. In this study, comparing the analysis results using the AEMM and Yassumii method long-term behaviors, the rationality of specified requirements is checked.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.697-700
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• 2006

The unique technology was developed to control the hydration heat of mass concrete by adding the Phase Change Material(PCM) to concrete. The PCM was designed to liquefy at 60 degrees and its size was limited under $10{\sim}30$ micro meters to be put in pores and to have no effect on compressive strength. In the hydration heat test, center temperature of the PCM specimen was reduced by 10 degrees without any difference in the strength. Even in the adiabatic temperature rise test, the final adiabatic temperature rise amount was reduced as much as 25% in comparison with the standard value in Korean Concrete Standard Specification.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.989-992
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• 2008

Recently, high-strength concrete has been frequently used for long-span bridges and high-rise buildings. Deflection of reinforced concrete structures is uncertain, so that many researchers have proposed various equations in order to predict deflection through experiments. Domestic concrete specification offers a procedure to evaluate deflection using effective moment of inertia which was proposed by Branson. However, it is inaccurate for high strength concrete compared to the method suggested in Eurocode 2 in that Eurocode 2 predicts deflection by using curvature integration of effective moment of inertia. In this study, experimental data about deflection of reinforced concrete beams were analyzed to compare domestic standard and Eurocode 2.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.417-422
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• 2000

In prestressed concrete structures, determining serviceability and safety it is important to exactly calculate effective prestress force acting on structures. for the determination of effective prestress force, friction loss of the prestressing tendon should be decided exactly, but it is very difficult to measure the exact prestress force on the site and there is no actual field data. Therefore the friction loss coefficient recommended by the specification is not verified. in this paper, the friction loss standard PSC-Beam will be investigated, and is will be found what kind of relationship between the specification and the site. The results from this study can be summarized as follows. For jacking at both ends, actual intial prestress force in the center section of PCS-Beam was about 1.61% larger than theoretical initial prestress force and for hacking at one end, actual initial prestress force was approximate 4.9% lower than theoretical initial prestress force. Thus, for the exact calculation of friction loss, friction coefficient should be modified according to jacking methods.

• Journal of the Korean Society of Safety
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• v.33 no.5
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• pp.60-69
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• 2018

This study aims to investigate in the assessment of salt damage conditions in concrete structures under marine environment conditions. It aims also to improve the durability of new concrete bridge through applying the life prediction method of salt damaged bridges. As measuring chloride contents of these bridges on the southwest coastal area, it is shown that the average amount of chloride on these surfaces close to shore is $10.5kg/m^3$. This figure is much higher than that of the Standard Specification for Concrete($1.5kg/m^3{\sim}2.5kg/m^3$). In contrast, it is shown the average amount of chloride on these surfaces in tide zone is $13.1kg/m^3$. Its figure is much lower than that of the Standard Specification for Concrete($20kg/m^3$). And the life of bridges is estimated about 17 years. To improve the durability for salt damage, these bridges are applied to surface treatment method which the replacement rate of furnace slag is 60%. Under this condition, it is expected to be 110 years. Consequently, it is clear that the use of slag replacement rate, surface treatment agent, and anti-corrosion agent to control chloride penetration effects of a submerge-based concrete bridge will be required.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.141-144
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• 2008

Deflection in terms of serviceability of reinforced concrete structures is considered as one of significant factor. Domestic concrete specification offers a procedure to evaluate deflection using effective moment of inertia at cracked section, which has been known as Branson's equation in ACI. Branson's equation was derived from statistical analysis of maximum deflection of flexural members, but is somewhat weak in no reflection of bond characteristics between reinforced bars and concrete, such as tension stiffening effect. Therefore, present code creates difference from actual deflection. In this study, experiments about deflection of RC beams was completed to compare domestic standard and Eurocode 2, which calculates deflection considering tension stiffening effect. Four RC beams were built and tested, and initial modulus of elasticity and tensile strength of concrete used in the test was calculated by each design standard.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.613-618
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• 2002

Steel slag produced in steel making process is divided with electric arc furnace slag and converter slag. Compared with the blast furnace slag, converter slag has the expansibility due to the reaction with water and free CaO. Therefore it is specified in Standard Specification for Concrete in Korea that steel slag aggregate must not be used in concrete. In this study, we treat electric arc furnace slag aggregate(EAFSA) for concrete before and after several aging process to reduce expansibility. The fundamental properties are measured, which are specific gravity, unit weight, abrasion value and immersion expansion ratio, as concrete aggregate. To understand the suitability of EAFSA for concrete, we made the concrete with EAFSA and then determined the strength and the volume change in EAFSA concrete. From the results EAFSA treated with steam aging process has potentiality for concrete aggregate.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.05a
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• pp.129-130
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• 2023

The compressive strength of concrete is greatly affected by the temperature inside the concrete at the initial age immediately after pouring. In the KCI Concrete Standard Specification, only the temperature correction strength (Tn) according to the curing temperature is applied in the mixing strength calculation formula, and mSn is not considered. The formula based on the Chrino model of the blast furnace slag concrete was calculated, and the strength of the structural concrete and the strength of the water cured specimen in the same mixture were compared with the predicted strength. As a result, the error between the predicted strength and the measured strength was greater in the structural concrete than in the concrete specimen.

• Journal of the Korea Institute of Building Construction
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• v.5 no.3 s.17
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• pp.91-99
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• 2005

It is required to study systematical on the concrete quality management to extend structure life because rebuilding effect is reducing under present condition of large sized and high stories structure. Concrete, which shows its intensity by hydrating action and a big change in quality according to hot weather and temperature, produces a lot of qualify problem under hot and cold weather Because of each specification and construction plan which does not have basic standard on site, concrete's quality is irregular and makes some defect. As a result, Daegu is turned out to be the longest area after investigating application period and days focused on 8 cities weather information about relationship between hot weather circumstance and construction environment. Therefore, we first surveyed the concrete material in the region and found out the problem of quality nanagement. Then figure out the way of solution. Moreover, we integrated concrete material quality management, which is applied differently to each site, to have equal quality and to reduce defect from construction site. And then, based on various test of construction condition and analysis of quality management item, we suggest effective concrete quality management to make concrete material construction standard guide and plan under hot weather.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.305-308
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• 2004

Cold weather concrete is the concrete which is used during construction under low-temperature' environment, and this kind of concrete has to be taken care not to be frozen in early ages of setting-hardening, It is specified in the Concrete Standard Specification(2003) as 'the cold weather concrete must be used on the weather condition under the average daily outdoor temperature below $4^{\circ}C$.' In this research, the mechanical characteristics and hydration heat on the cold weather concrete using high early strength portland cement were studied. As a result, the excellent quality was obtained and high early strength portland cement is expected to be used widely as the cold weather concrete.