• Proceedings of the Korea Concrete Institute Conference
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• 1989.10a
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• pp.63-67
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• 1989

Various studies have been done to investigate the effectiveness of lateral confinement of lower strength concrete(below 420kg/$\textrm{cm}^2$). But little research its effectiveness for high strength concrete. A certain concern has been arised that the beneficial effect of lateral confinement in high strength concrete may be different from that in lower strength. This study aimed to investigate that concern with different confinement spacing(D/2 : D/4). The results show that beneficial effects of spiral confinement are more pronounced for lower strength concrete as compared to higher strength concrete.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.04a
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• pp.323-328
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• 1997

The strength of concrete depends on factors of materials, composition and manufacturing method. Among these factors, preparatory experiments are to consider and analyze the factors on compressive strength of ultra-high strength concrete according to types of aggregate, binder content, water-binder ratio, and curing methods. And the final experiment to develop the ultra-high strength over 3,000kgf/$\textrm{cm}^2$ is based on these preparatory experiments. As the result of this final expriment. We could manufacture the ultra-high strength concrete with a marvelous compressive strength concrete with a marvelous compressive strength of 3,116kgf/$\textrm{cm}^2$. This study is to compare and analyze the manufacturing system of ultra-high strength concrete of 3,116kgf/$\textrm{cm}^2$ compressive strength in the side of material development of construction industry.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.549-552
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• 2006

Generally the ultra-high strength steel reinforced concrete has rich mix composition composed of high-strength type mineral admixtures and as a result of very low water-binder ratio(about under w/b=25%), it reveals ultra-high compressive strength(about over 100Mpa). Also, in order to obtain sufficient toughness after construction, we usually mix a large quantity steel fiber with ultra-high strength steel reinforced concrete therefore we must use proper mixer for workability. When we make the ultra-high strength steel reinforced concrete we need more long mixing time or much super-plasticizer than when we manufacture normal concrete. These bring about economical problems and performance deterioration. Therefore, in this study, in order to manufacture easily ultra-high strength steel reinforced concrete we develope a dedicated mixer for ultra-high strength steel reinforced concrete with high speed type. It carried out the examination for comparison between the dedicated and general type mixer, the analysis and counterplan of the point at issue when we manufacture ultra-high strength steel reinforced concrete by the dedicated mixer.

• Journal of the Korea Institute of Building Construction
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• v.4 no.2
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• pp.113-118
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• 2004

This study is a basic experiment on quality management of the compression strength of high strength concrete, aiming. at quality management of high strength mass concrete by giving the temperature hysteresis of the mass test pieces to managerial test pieces. Different from ordinary concrete, high strength concrete generally shows the temperature high rising caused by hydration heat inside the concrete. It is known that, in mass concrete, thermal stress occurs due to the difference in temperature between the inside and the outside, which causes a significant difference in compression strength between structure beams and managerial test pieces. It is also reported that there is a large difference between the compression strength of cylindrical managerial test pieces of standard underwater curing and the strength of structure beam concrete. Thus, this study made concrete test pieces in an optimal mix ratio for each strength level, and also created thermal insulation curing box and managerial test pieces. Then it carried out comparative analysis in relation to core strength and suggested equipment and a technique that can control the strength of high strength concrete mass more conveniently and accurately.

• KIEAE Journal
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• v.7 no.4
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• pp.105-111
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• 2007

As this study investigates the influence about type of transverse reinforcement, spacing of transverse reinforcement(s), volumetric ratios of transverse reinforcement(${\rho}s$) of ultra-high strength concrete columns. It try to offer to resonable basic data of the confined model for the ultra-high concrete of in reinforced concrete columns. Experimental tests with large scaled columns were conducted under concentric axial loads. The ultra-high strength concrete (100MPa) was used. From this test result, it evaluate influence of the strength enhancement and ductility enhancement, important variables about behavior of the confined concrete by confinement of ultra-high strength reinforced concrete.There are two ways to improve the confinement effect of high strength concrete columns through the increase of amounts and/or strength of transverse reinforcement.

• Journal of the Korean Society of Safety
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• v.32 no.5
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• pp.69-75
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• 2017

Structural safety evaluation for static strength of thin plate RC member with high strength concrete is conducted in this study. Static strengths were predicted and compared with the experimental values. Predicted values were calculated by the evaluation formula based on the punching shear behavior and the yield line theory which can appear in the plate members. Static load tests were carried out for the specimens with high strength concrete and the test results were compared with the required performance in design. The comparison results show that the specimens with high strength concrete have sufficient structural safety for flexural and punching shear performance required in design. High strength concrete specimens exhibited excellent strength despite their small thickness. The range of concrete strengths applied in this study was about 60 MPa to 100 MPa.

• Proceedings of the Korea Concrete Institute Conference
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• 1994.10a
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• pp.171-174
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• 1994

To reduce the size of structural members, high strength concrete has recently been utilized for structure such as ultra-high-rise buildings and prestressed concrete bridges in North America, and its compressive strength has gone up to 1300kg/$\textrm{cm}^2$. In Japan, research on high-strength concrete has been undertaken on a large scale by the national enterprise so-called New RC Project. And high-strength concrete with a design compressive strength over 450kg/$\textrm{cm}^2$ has recently been employed for high rised reinforced concrete building. As a result of the serious land availability situation of metropolitan areas in the world, buildings will become taller, and even higher strengths will be required. In the future, the utilization of high-strength concrete will spread widely through the development of new structural concepts, application of steels of a higher yield stress, silica fume, and other new materials. Considering these circumstance, the aim of this experimental study is to develop ultra-high-strength concrete with compressive strength over 1800kg/$\textrm{cm}^2$ with domestic current materials. There are so many factors which influence the manufacturing of ultra-high-strength concrete. The experimental factors selected in this study are mixing methods, curing methods, water-binder ratio, maximum size of coarse by silica fume. The results of this experimental study show that it is possible to develop the ultra-high-strength concrete with compressive strength over 1700kg/$\textrm{cm}^2$ at 28days, 1800kg/$\textrm{cm}^2$ at 56 days.

• Proceedings of the Korea Concrete Institute Conference
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• 1991.10a
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• pp.21-25
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• 1991

For the purpose of improving the compressive strength of concrete, the high strength concrete which have the compressive strength about 800kg/$\textrm{cm}^2$ were made by using silica fume and high range water reducing admixture on reducing the water-cement ratio. But the facts that the slump loss of high strength concrete was high and the tensile strength and elastic modulus were not improved enough are indicated to problems which must be solved.

• Magazine of the Korea Concrete Institute
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• v.7 no.2
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• pp.155-164
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• 1995

This study was performed to get high strength of the precase concrete adopting a steam curing by using a gypsum-admixture for the high strength concrete. The superplasticizer was used to compensate low slump of base concrete keeping its slump up about $6{\pm}1cm$. To examine the property for strength revelation of concrete using admixtures for a high strength concrete, steam and standard curing were compared each other. Test results were shown that admixtures for high strength concrete were more effective in steam curing than standard curing. On the condition that the unit cement content is about $530{\sim}600kg/m^3$, the compressive strength of concrete replacing by 10% of the admixture was obtained over $65Okgf/cm^2$, which was increased as 1.3 times as that for the nonreplacement. When the admixture was replaced to 15-30%, the compressive strengh was obtained over $700kgf/cm^2$ which was increased as 1.4 - 1.5 times. Therefore, the admixture for high strength concrete, being effective in steam curing, was more efficient to get a high strength concrete using only steam curing instead of an autoclave curing for the secondary products of cement.

• Structural Engineering and Mechanics
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• v.41 no.3
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• pp.407-420
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• 2012

This study investigated possible ways to replace conventional stirrups used on high-strength concrete members with improved reinforcing materials. Headed bar and high-strength steel were chosen to substitute for conventional stirrups, and an experimental comparison between the shear behavior of high-strength concrete large beams reinforced with conventional stirrups and the chosen stirrup substitutes was made. Test results indicated that the headed bar and the high-strength steel led to a significant reserve of shear strength and a good redistribution of shear between stirrups after shear cracking. This is due to the headed bar providing excellent end anchorage and the high-strength steel successfully resisting higher and sudden shear transmission from the concrete to the shear reinforcement. Experimental results presented in this paper were also compared with various prediction models for shear strength of concrete members.