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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of the Korea Concrete Institute
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Korea Concrete Institute
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Volume & Issues
Volume 20, Issue 6 - Dec 2008
Volume 20, Issue 5 - Oct 2008
Volume 20, Issue 4 - Aug 2008
Volume 20, Issue 3 - Jun 2008
Volume 20, Issue 2 - Apr 2008
Volume 20, Issue 1 - Feb 2008
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Hydration Characteristics according to First Curing Condition in Solid Hydrated by Hydro-Thermal Synthesis Reaction
Kim, Jin-Man ; Jung, Eun-Hye ; Park, Sun-Gyu ;
Journal of the Korea Concrete Institute, volume 20, issue 5, 2008, Pages 543~548
DOI : 10.4334/JKCI.2008.20.5.543
Solid hydrated by hydro-thermal synthesis reaction is cured two times, the first curing is the steam curing at atmospheric pressure and the second one is a high-pressure steam curing, that is autoclaving. Steam curing is to acquire the proper strength for the resistance of treatment in the first curing process, it was not evaluated properly so far. Because of ignorance about curing, some engineers even think that the dry curing is better than the steam curing. The relation between compressive strength of solid hydrated by hydrothermal synthesis reaction and curing condition are presented in this paper. In order to investigate the effect of curing on the strength properties of specimen, the hydration behavior of solid hydrated by hydro-thermal synthesis reaction has been studied over curing condition using XRD, DT-TGA and porosimeter, SEM analysis technique. The results show that the specimens which are cured with blended method of dry and steam curing appear to have better strength properties than that of dry curing and steam curing. Also, there are significant difference of hydration behavior among curing condition in the solid hydrated by hydro-thermal synthesis reaction.
Hydration Heat and Shrinkage of Concrete Using Hwangtoh Binder
Kang, Sung-Soo ; Lee, Seong-Lo ; Hwang, Hey-Zoo ; Cho, Min-Chol ;
Journal of the Korea Concrete Institute, volume 20, issue 5, 2008, Pages 549~555
DOI : 10.4334/JKCI.2008.20.5.549
In this paper, the applicability of Hwangtoh, as an alternative of cement paste, is investigated for the solution of internal heat and shrinkage caused by the hydration of cement paste. Several small-sized specimens of Hwangtoh and ordinary portland concrete (OPC) were compared as to compressive strength, heat of hydration, and shrinkage strain. Moreover, the applicability to the construction structures was reviewed through the test of large-size specimens. The 28-day compressive strength of Hwangtoh concrete (HBC), ranged 18 to 33 MPa, can reach that of OPC. Not only the maximun internal temperature of HBC was read about 1/4 of OPC as it is cured, but also its shrinkage decreased more than the OPC did. Therefore, Hwangtoh binder is more favorable than cement binder in terms of its hydration heat and shrinkage under the construction of concrete.
Optimum Abrasing Condition for Recycled Fine Aggregate Produced by Low Speed Wet Abraser Using Sulfur
Kim, Jin-Man ; Kim, Ha-Seog ; Park, Sun-Gyu ; Kim, Bong-Ju ; Kwak, Eun-Gu ;
Journal of the Korea Concrete Institute, volume 20, issue 5, 2008, Pages 557~563
DOI : 10.4334/JKCI.2008.20.5.557
Recently, the amount of disposed construction materials like demolished concrete is growing fast and the shortage of natural concrete aggregate is becoming serious. Therefore, recycling of aggregate extracted from the demolished concrete is getting important and use of the recycled aggregate for concrete has been seriously considered. However, the use of the recycled aggregate even for low performance concrete is very limited because recycled aggregate which contains large amount of old mortar has very low quality. Therefore, removing the paste sticked to the recycled aggregate is very important in the manufacturing of high quality recycled aggregate. We have studied a series of research according to complex crushing method, which is removed the ingredient of cement paste from recycled fine aggregate using both the low speed wet abrasion crusher as mechanical process and the acid treatment as chemical processes. This paper is to analyze the quality of the recycled fine aggregate produced by those complex method and investigate optimum manufacturing condition for recycled fine aggregate by the design of experiments. The experimental parameters considered are water ratio, coase aggregate ratio, and abrasion time. As a result, data concerning the properties of recycled sand were obtained. It was found that high quality recycled fine aggregate could be to obtain at the condition of the fifteen minute of abrasion-crusher time and the over 1.0 of recycled coarse aggregate ratio.
Behaviors of a Vault Door Made of Ultra High Performance Concrete and Strengthening Structures Subjected to Extreme Impact Load and Ultra High Heat
Oh, Seok-Min ; Kim, Tae-Wan ; Hong, Sung-Nam ; Park, Sun-Kyu ;
Journal of the Korea Concrete Institute, volume 20, issue 5, 2008, Pages 565~572
DOI : 10.4334/JKCI.2008.20.5.565
It is a trend to increase safekeeping properties in financial company as the world economy situation has been globalized and advanced. The development of a securable vault door resisting to malicious trespass is needed. Therefore, this study focuses on developing high performance concrete placed at the inside of the vault door, and all materials used in this study is easy to obtain in domestic considering economic competitiveness. The compressive strength over 170 MPa was targeted, and structurally strengthening was also planned in order to resist to over
heating by torch and extreme impact loading by hammer drilling machine. Several types of fibers and reinforcing structures were used in order to resist those external heating and loading. This purpose was required to satisfy UL 608 standard of a vault door. Consequently, the result from this study is expected to be applied to construction field of major facilities, which should guarantee the safety from an external attack such as terror.
Experimental Study on the Shear Strength of Form Tie Connector Linked by Stud Coupler
Seo, Soo-Yeon ; Kim, Seoung-Soo ; Yoon, Yong-Dae ; Ha, Gee-Joo ;
Journal of the Korea Concrete Institute, volume 20, issue 5, 2008, Pages 573~581
DOI : 10.4334/JKCI.2008.20.5.573
In general, conventional sheeting H-pile is often used as a temporary member installed upon construction of outer retaining wall at basement floor. In CBW (composite basement wall), R/C basement wall is combined with H-Pile and resists lateral soil pressure together. This paper presents an experimental results of push out shear test of CBW with stud coupler as shear connectors to combine H-Pile with R/C wall six specimens with different diameter of FT (form tie) and arrangement of shear connectors were tested to evaluate the shear capacity of the composite wall. Test results showed that shear strength increased with diameter of FT. The shear strength of shear connector in CBW could be suitably predicted by using the previous equations codified in the codes. Best correlation, especially, was found when the calculation result by the formula in AISC 360-05 was compared to test one.
Evaluation for Mechanical Properties of High Strength Concrete at High Temperature by Stressed Test and Unstressed Test
Kim, Gyu-Yong ; Kim, Young-Sun ; Lee, Tae-Gyu ; Park, Chan-Kyu ; Lee, Seung-Hoon ;
Journal of the Korea Concrete Institute, volume 20, issue 5, 2008, Pages 583~592
DOI : 10.4334/JKCI.2008.20.5.583
Recently, the effects of high temperature on compressive strength, elastic modulus and strain at peak stress of high strength concrete were experimentally investigated. The present study is aimed to study the effect of elevated temperatures ranging from 20 to 700 on the material mechanical properties of high strength concrete of 40, 60, 80 MPa grade. In this study, the types of test were the stressed test and stressed residual test that the specimens are subjected to a 25% of ultimate compressive strength at room temperature and sustained during heating and when target temperature is reached, the specimens are loaded to failure. And another specimens are loaded to failure after 24 hour cooling time. Tests were conducted at various temperatures (
) for concretes made with W/B ratios 46%, 32% and 25%. Test results showed that the relative values of compressive strength and elastic modulus decreased with increasing compressive strength grade of specimen and the axial strain at peak stress were influenced by the load before heating. Thermal strain of concrete at high temperature was affected by the preload level as well as the compressive strength. Finally, model equation for compressive strength and elastic modulus of heated high strength concrete proposed by result of this study.
A Fundamental Study on the Correlationship between Hydration Heat and Autogenous Shrinkage of High Strength Concrete at an Early Age
Kim, Gyu-Yong ; Lee, Eui-Bae ; Koo, Kyung-Mo ; Choi, Hyeong-Gil ;
Journal of the Korea Concrete Institute, volume 20, issue 5, 2008, Pages 593~600
DOI : 10.4334/JKCI.2008.20.5.593
In this study, to analyze the correlation between hydration heat and autogenous shrinkage of high strength concrete at an early age, hydration heating velocity and autogenous shrinking velocity as quantitative coefficients which represent the main properties of hydration heat and autogenous shrinkage were proposed. Two coefficients were calculated by statistical analysis and were equal with the regression coefficient. The complemented semi-adiabatic temperature rise test as test method to evaluate the hydration heat and autogenous shrinkage of concrete were proposed. In results of proposed test and analysis method, it was possible that early age properties of hydration heat and autogenous shrinkage of concrete were expressed numerically, and autogenous shrinkage was represented by equation with coefficients of hydration heat.
An Experimental Study on the Flexural Behavior of RC Beams Strengthened with NSM and EBR CFRP Strips
Lim, Dong-Hwan ;
Journal of the Korea Concrete Institute, volume 20, issue 5, 2008, Pages 601~609
DOI : 10.4334/JKCI.2008.20.5.601
The purpose of this study is to investigate the flexural strengthening effectiveness for the beams combined reinforced with NSM CFRP strips and EBR CFRP strips. To accomplish this objective, a total of nine concrete T beams were tested. From this study, it is found that the flexural stiffness and strength of the beams combined reinforced with NSM and EBR strips were significantly improved compared to the beams strengthened only with NSM CFRP strip. The maximum increase of flexural strength was 347% compared to the beam without CFRP strip. Failure of the beam combined reinforced with NSM and EBR strips (T shape) is initiated by debonding of EBR strips attached on the bottom face, and it was succeeded a part of separatio-n of NSM strips along the longitudinal direction and secondly failure of NSM strips was occurred, eventually sudden explosive failure with the separation of concrete cover in the shear region. This result shows that the NSM and EBR strips have good combination to resist applied load and the combined reinforcement with NSM and EBR strips can redistribute appropriately the total stress subjected concrete beam to the EBR and NSM strips.
An Experimental Study on the Performance of Compression-Type Anchor for CFRP Tendons
Jung, Woo-Tai ; Lee, Seung-Joo ; Park, Young-Hwan ;
Journal of the Korea Concrete Institute, volume 20, issue 5, 2008, Pages 611~618
DOI : 10.4334/JKCI.2008.20.5.611
CFRP (carbon fiber reinforced polymer) tendons can be used as an alternative to solve the corrosion problem of steel tendons. Since CFRP tendons are vulnerable to transverse pressure and stress concentration, the conventional anchorage system used for steel tendons can create an unreliable load carrying capacity and may result in a premature failure. Therefore, it is necessary to develop the anchorage system that is well suited for CFRP tendons. There are many types of anchorage systems for CFRP tendons, which can be classified into three types: wedge-type anchorage, bond-type anchorage, and compression-type anchorage. This paper deals with the compression-type anchorage system manufactured through swaging technology. Based on the previous test results performed by the authors, the dimension of anchorage sleeve, the use and non-use of the insert, and the compression pressure on the sleeve have been selected as the major parameters affecting the performance of the compression-type anchorage. Some anchorage sleeves have been tapered to reduce the stress concentration. Test results revealed that the performance of the anchorage system depends mainly on the dimension and the compression pressure. It has been verified that the tapered sleeve can effectively reduce the stress concentration.
Flexural Behavior of Hwangtoh Concrete Beams with Recycled PET Fiber
Kim, Sung-Bae ; Nam, Jin-Won ; Yi, Na-Hyun ; Kim, Jang-Jay-Ho ; Choi, Hong-Shik ;
Journal of the Korea Concrete Institute, volume 20, issue 5, 2008, Pages 619~626
DOI : 10.4334/JKCI.2008.20.5.619
There have been numerous studies to develop eco-friendly concrete. The attempt to reduce the amount of cement usage is suggested as one of the solutions for eco-friendly concrete. To reduce the amount of cement usage, the pozzolan-reaction materials such as ground granulated blast furnace slag, fly ash, and meta kaolin are widely used as the mineral admixture. Hwangtoh which deposited broadly in Korea is a well known eco-friendly material and the activated Hwangtoh with pozzolan-reaction can be practically used as a mineral admixture of concrete. Meanwhile, PET fiber made of recycled PET bottle is a type of recycled material, which can be used to control micro cracks in concrete. But the study about concrete mixed with recycled PET fiber is insufficient and the research of Hwangtoh concrete mixed with PET fiber is urgently needed presently. In this study, experiment and analysis flexural behavior of Hwangtoh concrete blended with recycled PET fiber are carried out. The results are discussed in detail.
Concrete Optimum Mixture Proportioning Based on a Database Using Convex Hulls
Lee, Bang-Yeon ; Kim, Jae-Hong ; Kim, Jin-Keun ;
Journal of the Korea Concrete Institute, volume 20, issue 5, 2008, Pages 627~634
DOI : 10.4334/JKCI.2008.20.5.627
This paper presents an optimum mixture design method for proportioning a concrete. In the proposed method, the search space is constrained as the domain defined by the minimal convex region of a database, instead of the available range of each component and the ratio composed of several components. The model for defining the search space which is expressed by the effective region is proposed. The effective region model evaluates whether a mix-proportion is effective on processing for optimization, yielding highly reliable results. Three concepts are adopted to realize the proposed methodology: A genetic algorithm for the optimization; an artificial neural network for predicting material properties; and a convex hull for evaluating the effective region. And then, it was applied to an optimization problem wherein the minimum cost should be obtained under a given strength requirement. Experimental test results show that the mix-proportion obtained from the proposed methodology using convex hulls is found to be more accurate and feasible than that obtained from a general optimum technique that does not consider this aspect.
Tensile Properties and Adhesion of Hybrid-Type Anti-Corrosion Polymer Cement Slurry
Jo, Young-Kug ;
Journal of the Korea Concrete Institute, volume 20, issue 5, 2008, Pages 635~642
DOI : 10.4334/JKCI.2008.20.5.635
In recent years, epoxy-coated reinforcing bars have been widely used in order to prevent the corrosion of ordinary reinforcing bar. However, they have a bad balance between performance and cost. Especially, they have a brittleness properties, low bond strength to cement concrete and no good bend-ability in the field. The purpose of this study is to evaluate the tensile properties and adhesion of hybrid-type anti-corrosion polymer cement slurry (PCS). PCSs are prepared with four types polymer dispersions using fly ash and silica fume, and tested for proper coating thickness, tensile properties, adhesion to steel plate and bend-ability. From the test results, the viscosity of PCS is effected by polymer dispersion types, and is a little decreased by using fly ash. The coating thickness of PCS has a proper thickness at polymer-binder ratio of 100%. It is apparent that the coating thickness has various values according to viscosity of PCS, water-binder ratio and polymer-binder rato. PCS has a good various anticorrosion properties and physical properties such as tensile strength, adhesion and bend-ability. It is also recommended that proper coating thickness to reinforcing bar is in the ranges of 150 to
for bond strength, adhesion and bend-ability. It is also expected that the coated reinforcing bar using PCS is widely used instead of epoxy coated reinforcing bar in the industrial field.
Dynamic Response of Seismically Isolated High-Story Buildings according to Earthquake Records
Lee, Hyun-Ho ;
Journal of the Korea Concrete Institute, volume 20, issue 5, 2008, Pages 643~651
DOI : 10.4334/JKCI.2008.20.5.643
The purpose of this study is to evaluate seismic capacity of seismically isolated building according to the earthquake motion record selection method. To analyze the seismic behavior, 20-story building is designed, which has base isolation system. The using earthquake motion record were selected by two categories. The one is a proposed earthquake record according to soil type and response spectrum shape, and the other is a well known earthquake events such as El Centro (1940). The time history analysis results of base isolation buildings be induced difference results according to each ground motion records. Therefore detailed guidelines for the ground motion records selection method must be prepared. And the response of isolation story displacement and shear force show good seismic performance in consideration of the proposed earthquake records.
A Study on the Development of Sound Absorption Material Using Perlite for Noise Barrier Wall
Jo, Young-Kug ; Yang, Ju-Kyung ;
Journal of the Korea Concrete Institute, volume 20, issue 5, 2008, Pages 653~660
DOI : 10.4334/JKCI.2008.20.5.653
The purpose of this study is to analyze the optimal mix design of the sound absorption material that is made from perlite and various binder systems for noise barrier wall. The polymer cement slurry which is made from two types of polymer dispersions, and silicone type inorganic material are used as binder. The test specimens are prepared with various polymer cement ratios, binder ratios, and tested for strengths, freezing and thawing and sound absorption performance by the tube and the reverberation room methods. From the test results, the difference of sound absorption coefficient by the tube method is a little recognized, however, noise reduction coefficient (NRC) of test specimens bound by the polymer cement slurry is in the ranges of 0.48 to 0.51. They are a little higher than those bound by cement only, and are lower values than recommended value of 0.7 by the Ministry of Environment. However, the sound absorption coefficient of test specimens at low frequency range of 250 to 500 Hz by reverberation room method shows very high values as 0.84 to 1.00, and 0.57 to 0.77 at the high frequency. The test specimens with polymer cement slurry binder have a good balance between performance and cost, and have proper properties in strengths, freezing and thawing resistance as sound absorption material for noise barrier wall. It is apparent that the good sound absorption material can be produced according to the optimum mix design that is recommended from this study.
An Experimental Study on Properties of Concrete Using Latent Heat Binder
Kim, Yong-Ro ; Kim, Do-Su ; Khil, Bae-Su ; Kim, Ook-Jong ; Lee, Do-Bum ;
Journal of the Korea Concrete Institute, volume 20, issue 5, 2008, Pages 661~668
DOI : 10.4334/JKCI.2008.20.5.661
It is necessary to develop a new technology for effectively reducing hydration heat and controlling thermal cracking caused increasing construction of large size massive concrete structures such as mat foundation of high-rise building, grandiose bridge, and LNG tank. Therefor, to develop a new technology for reducing hydration heat of large size massive concrete in this study, after developing the latent heat binder for controling hydration heat of concrete by application of latent heat material, it was investigated basic properties and durability such as slump, air content and compressive strength, shrinkage properties, permeability, freezing and thawing resistance, corrosion, and hydration heat generation properties of concrete using latent heat binder. As a test result, it was confirmed that latent heat binder was not affected adversely the basic property and durability of concrete, and was advanced on the reduction of hydration heat and control of thermal crack. It is expected to be applied as the excellent technology on the management of hydration heat and thermal crack in large size mass concrete structures.