• Proceedings of the Korea Concrete Institute Conference
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• 1996.04a
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• pp.357-362
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• 1996

The objective of this study is to investigate material properties and quality control of cast-in-place high strength concrete. High strength concrete with a design strength of 420 kgf/$\textrm{cm}^2$ is successfully produced at a ready-mixed concrete plant, and placed at a tall building. Many laboratory and field tests are carried out for the successful construction of the reinforced high strength concrete building. As the results of this study, the average actual 28-day compressive strength is 513 kgf/$\textrm{cm}^2$ and the coefficient of variation is 6.8%. The placing speed is comparable to normal strength concrete, however, the pump pressure is higher than that of normal strength concrete. To prevent cracks of massive and long concrete members, the control of hydration heat and shrinkage is very important.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05a
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• pp.9-14
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• 2005

The Burj Dubai Project will be the tallest structure ever built by man; when completed the tower will be more than 700 meter tall and more than 160 floors. The early integration of aerodynamic shaping and wind engineering considerations played a major role in the architectural massing and design of this residential tower, where mitigating and taming the dynamic wind effects was one of the most important design criteria. This paper presents a brief overview of the structural system development and considerations of the tower and discusses the construction planning of the key structural components of the tower.

• Proceedings of the Korea Concrete Institute Conference
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• 1992.10a
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• pp.100-105
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• 1992

While there are many researches in high-strength concrete recently, average strength required is the level of 400kg/$\textrm{cm}^2$ 28days compressive strength yet. For the effective using of high strength concrete, high strength concrete of 600 to 800kg/$\textrm{cm}^2$ 28days compressive strength must be accepted, But in this high strength concrete, due to much cement content, there are the problems of high hydration heat, high viscosity and economical efficiency. To solve these problems, it is suggested the method that replacement some of cement content as flyash up-to-dately. Therefore, the aim of this study is to develop high strength concrete of 800kg/$\textrm{cm}^2$ 28days compressive strength containing fly ash. This paper is the part I that analyze the testing results of fresh concrete in various aspects.

• Proceedings of the Korea Concrete Institute Conference
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• 1994.10a
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• pp.71-76
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• 1994

Recently, constructions of huge reinforced concrete structures such as nuclear power stations have been increased. When massive concrete is placed, cracking due to the hydration heat of cement is recognized as a major problem. The development of thermal stress is influenced by the structure shape and the constraint conditions, and cracks usually occure from tensile stresses which developed due to temperature drop. In this study a protocol specimen is made to examine the distribution of temperature and thermal stress of reaction wall of Daewoo Institute Construction Technology. The size of the specimen is made by considering minimum size of real structure. In this study, concrete strain gauge, concrete stress gauge, concrete non-stress gauge, and thermocouples, are instrumented to measure thermal stress in massive concrete structure. A new measuring technique is proposed to calculate thermal stress.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.144-147
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• 2004

In this paper, field application of mass concreting using super retarding agent(SRA) are discussed based on setting. time difference with SRA in big discount market in Chongju. Mechanical and physical properties of .concrete are investigated. Temperature history of concrete is also measured. Slump and air content meet the requirement of target value. Compressive strength of concrete exceeded the nominal strength with 24MPa. Compressive strength of SRA concrete is higher than that of plain concrete by about $3\~4\%$. For temperature history, peak temperature of concrete at middle section at top concrete layer reached $49.6^{\circ}C$ within 24hours, and at bottom concrete layer, $54.6^{\circ}C$ within 42hours. Based on the naked eye's observation, no crack was found at mass concrete.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2002.10a
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• pp.153-156
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• 2002

The purpose of this research was to evaluate on the properties of fresh and hardened high-performance concrete(HPC) incorporating high-reactivity metakaolin(HRM). Setting time, heat of hydration, compressive strength, resistance to chloride-ion penetration, and repeated freezing and thawing test were carried out in order to investigate the properties of fresh and hardened state concrete. The properties of the HRM concrete were also compared with those of the portland cement concrete and silica fume(SF) concrete. The laboratory test results indicate that HRM material can be used as a supplementary cementitious material to produce high-performance concrete.

• Proceedings of the Korea Concrete Institute Conference
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• 1996.04a
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• pp.95-100
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• 1996

This paper presents the experimental study on hardening process of high-strength and high-flowable concrete. The experiments were performed to investigate any unfavorable construction situations since the actual concrete placement has been scheduled in cold weather period, so that the high quality concrete construction is convinced to be successfully carried out. The tests were conducted using 600nm and 1000nm height of steel tube to simulate the practical concrete filled steel tube columns according to the following variables as: the categories of chemical admixtures, curing temperatures and curing schemes. The test results were analyzed in terms of hardening speed, internal heat of hydration and history of strength gain. This paper emphasizes the importance of curing schemes on durability and the use of hardening accelerators on strength gain.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.118-121
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• 2000

CFRD (Concrete Faced Rockfill Dam) face slab concrete has a much capability to occur crack due to drying shrinkage, hydration heat and bas compaction etc. Because of crack of concrete induce structural problem and decrease durability of concrete, it is need to reduce crack of concrete. This is an experimental study to analyze the Control Property of Plastic Shrinkage Crack for CFRD face slab concrete. For this purpose, it was investigated and analyzed the engineering properties of plain concrete and using admixtures (polypropylene fiber, fly-ash) according to test result As the result, it was found that crack width and area of concrete using admixtures less than of plain concrete.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.10b
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• pp.928-933
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• 1998

The temperature and stress behaviour of mass concrete pier at early ages was analysed based on the finite element method. The pier investigated is a three-dimensional structure of which the cross-sectional shape varies from a circle to an ellipsoid along the longitudinal axis. In order to obtain the transient temperature and stress distributions in the structure, a three dimensional method was adopted, because the structure of this type cannot be modeled accurately by a two-dimensional method. Temperature analysis was performed by taking into consideration of the cement type and content, boundary and environment conditions including the variations of atmospheric temperature and wind velocity. The results of this study may be useful for the temperature control to restrain thermal cracking and the construction management to design the resonable curing method of mass concrete structure.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2013.11a
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• pp.186-187
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• 2013

Recently, high fluidity concrete is becoming more prevalent. High fluidity concrete uses admixture or thickener in order to prevent separation of materials due to increased fluidity, and, especially, BS is becoming more use for reduced heat of hydration and improved long-term strength. This study examined the effect of BS on fluidity of cement paste from a rheological viewpoint. As for BS types, materials equivalent to 1 types of KS F 2563 and the cement mass was substituted by 20, 40, 60, 80%.