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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 25, Issue 6 - Dec 2013
Volume 25, Issue 5 - Oct 2013
Volume 25, Issue 4 - Aug 2013
Volume 25, Issue 3 - Jun 2013
Volume 25, Issue 2 - Apr 2013
Volume 25, Issue 1 - Feb 2013
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Mechanism of Strength Development in Ultra High Strength Concrete Using the Electric Arc Furnace Oxidizing Slag as Fine Aggregate
Lee, Seung-Heun ; Lim, Doo-Sub ; Lee, Seung-Hoon ; Lee, Joo-Ha ;
Journal of the Korea Concrete Institute, volume 25, issue 1, 2013, Pages 3~9
DOI : 10.4334/JKCI.2013.25.1.003
In ultra high strength concrete, when electric arc furnace oxidizing slag is substituted for sea sand as fine aggregate, compressive strength was improved about 15 MPa. To figure out the cause of the improvement in compressive strength, this study considered the dissolution characteristics of Ca component in fine aggregate and examined the microstructure, porosity, microhardness, and Ca/Si mole ratio on the interface of fine aggregate and paste. And to examine the mechanism of strength improvement resulted from the shape of fine aggregate, this study measured the surface roughness of fine aggregate with AFM. According to the result of this experiment, the mechanisms of strength improvement in ultra high strength concrete resulted from the use of electric arc furnace oxidizing slag as fine aggregate can be divided into chemical and physical mechanisms. In the chemical mechanism, the soluble Ca component contained in electric arc furnace oxidizing slag is dissolved and forms a hydrate between fine aggregate and paste to improve the interlocking strength of fine aggregate-paste. Also, it makes the microstructure around the fine aggregate. And in the physical mechanism, electric arc furnace oxidizing slag has a twice greater surface roughness than sea sand, so the interlocking strength between fine aggregate and paste increases, which contributes to the development of compressive strength.
An Experimental Study on Mechanical Properties of Hybrid Fiber Reinforced Concrete Pavement
Park, Jong-Sup ; Choi, Sung-Yong ; Jung, Woo-Tai ; Park, Young-Hwan ;
Journal of the Korea Concrete Institute, volume 25, issue 1, 2013, Pages 11~18
DOI : 10.4334/JKCI.2013.25.1.011
Cement concrete pavement offers long-term service life and excellent applicability for heavy traffic. It is easier to purchase and more durable and economical than the asphalt pavement. However, it is difficult to repair and rehabilitate compared to the asphalt pavement when it comes to the maintenance problem. Since the crack is the main reason of the damage of concrete pavement, it is necessary to control the early and long-term crack in the concrete pavement. In this experimental study, the basic performance tests have been carried out to investigate the effect of hybrid fibers which were composed of micro fibers with small diameter and high aspect ratio and macro fibers with large diameter and low aspect ratio on the concrete pavement, in which lower water ratio and larger aggregates were used compared to the general concrete mixture. The test results showed that the flexural strength and toughness of concrete pavement mixture have been increased with the use of hybrid fibers in the concrete pavement mixture, even though they were less effective compared to the normal concrete mixture. It was found that the hybrid fibers were effective to control the early shrinkage of the concrete pavement which is one of the main reasons of the damage in the concrete pavement.
Evaluation of Axial Strains of Reinforced Concrete Columns
Lee, Jung-Yoon ; Kim, Min-Ok ; Kim, Hyung-Beom ;
Journal of the Korea Concrete Institute, volume 25, issue 1, 2013, Pages 19~28
DOI : 10.4334/JKCI.2013.25.1.019
The longitudinal axial strain in the plastic hinge region of reinforced concrete (RC) columns influences on the structural behavior of RC structures subjected to reversed cyclic loading. This strain decreases the effective compressive strength of concrete and increases the lateral displacements between stories by causing the elongation of member length. This paper investigated the effects of the axial force on the elongation of a RC member by using a sectional analysis of RC members. The analytical and experimental results indicated that the axial force decreased the axial strain in the plastic hinge region of RC columns. In this study, a model was proposed to predict the axial strain of RC columns. The proposed model considering the effects of axial force ratio consisted of three path types ; Path 1-loading region, Path 2-unloading region, and Path 3-reversing cyclic loading region. The axal strains predicted by the proposed model were compared with the test results of RC columns with various axial force ratios, and agreed reasonably with the observed longitudinal strains.
Analysis of Nonlinear Torsional Behavior for High Strength Reinforced Concrete Structure Using 3-Dimensional Lattice Model
Kwon, Min-Ho ; Seo, Hyun-Su ; Lim, Jeong-Hee ; Kim, Jin-Sup ;
Journal of the Korea Concrete Institute, volume 25, issue 1, 2013, Pages 29~36
DOI : 10.4334/JKCI.2013.25.1.029
Because of earthquakes that have recently struck, seismic design criteria that considered performance of structure were included in the design concepts. Thus, a simple analysis tool is needed to predict the strength and ductility of RC structures. In this study, three-dimensional lattice model was developed to expand the two-dimensional lattice model. Torsional analysis of the structure was done to evaluate the developed three-dimensional lattice model. Lattice model was evaluated by comparing analytical results with experimental results. Lattice element size was evaluated using the results of analysis. Torsional analysis results, using three-dimensional lattice model, show that the results are relatively consistent with the experimental values.
Bond Strength of Near Surface-Mounted FRP Plate in Concrete Corresponding to Space and Bond Length
Seo, Soo-Yeon ; Kim, Min-Sik ;
Journal of the Korea Concrete Institute, volume 25, issue 1, 2013, Pages 37~43
DOI : 10.4334/JKCI.2013.25.1.037
Recently, experimental and analytical researches have been performed in order to find interface failure between FRP plate and concrete in near surface-mounted (NSM) retrofit using FRP plate. As a result, it was found that the bond strength between concrete and NSM FRP plate had a close relationship with shape of FRP, concrete compressive strength and bond length. However, research need is increasing about another factors such as suitable space of FRP plate and group effect. In this study, therefore, a bond test was performed with aforementioned factors and compared with a previous equation to verify its suitability for predicting bond strength of NSM FRP plate. From the test, it was found that the bond strength increased according to the increase of space of NSM FRP plates even if its bond length was same. The splitting failure of concrete governed when space of FRPs was too narrow and it changed to FRP's tensile failure with increase of the space. From the evaluation of test specimens using previous equation, it was found that the bond strength could be predicted properly with consideration of group effect.
Critical Temperature for Inter-Laminar Shear Strength and Effect of Exposure Time of FRP Rebars
Moon, Do-Young ;
Journal of the Korea Concrete Institute, volume 25, issue 1, 2013, Pages 45~51
DOI : 10.4334/JKCI.2013.25.1.045
Short beam tests of GFRP and CFRP specimens exposed to high temperature were conducted to measure the inter-laminar shear strength. For the phase I test, the exposure time and temperature were varied to measure reduction in the strength due to the applied conditions. As a results, the critical temperature was found to
for the both FRP reinforcements. The high temperature, which causes 50% loss of inter-laminar shear strength, is defined as the critical temperature in this study. It should be noted that the critical temperature for the inter-laminar shear strength is mainly dependent on resin properties not on fiber type. In the phase II test, the effect of exposure time was investigated at intervals of 0.25hour for the critical temperature. All test results demonstrate that the exposure time effect is not significant compared to the maximum exposure temperature, but it is not negligible and, moreover, is significant at the critical temperature.
Experimental Evaluation on Bond Strengths of Reinforcing Bar in Coils with Improved Machinability during Straightening Process
Chun, Sung-Chul ; Choi, Oan-Chul ; Jin, Jong-Min ;
Journal of the Korea Concrete Institute, volume 25, issue 1, 2013, Pages 53~61
DOI : 10.4334/JKCI.2013.25.1.053
A new deformation of reinforcing bar in coils was proposed to improve a machinability of straightening process, which has crescent-shaped transverse ribs with an inclination angle of 50 degrees, a crest width of
, and a flank inclination of 55 degrees. The proposed deformation can increase contact area between a surface of re-bar and a groove of a roller during a straightening process and, therefore, it might reduce a damage of ribs, improve a final straightness, and enhance an efficiency of the straightening process. Splice tests were conducted to evaluate bond strengths of three types of re-bar in coils including the proposed re-bar, of which the inclination angles of transverse ribs were 50, 60, and 90 degrees, respectively. Test results show that the re-bars in coils have higher bond strengths than predicted strengths by equations of Orangun et al., ACI 408, and KCI by at least 10%. Correlation coefficients of bond strengths between a straight bar and re-bars in coils are 0.94 and more. Consequently, equations of the KCI code for determining development and splice lengths can be applied to the tested re-bars in coils.
Torsional Behavior of Hybrid Truss Bridge according to Connection Systems
Jung, Kwang-Hoe ; Lee, Sang-Hyu ; Yi, Jong-Won ; Choi, Ji-Hun ; Kim, Jang-Ho Jay ;
Journal of the Korea Concrete Institute, volume 25, issue 1, 2013, Pages 63~72
DOI : 10.4334/JKCI.2013.25.1.063
HTB (hybrid truss bridge) steel truss webs instead of concrete webs in prestressed box girder bridges has been widely used in, because of its structural benefit such as relatively less self-weight and good aesthetics due to open web structure. Since the core technology of this bridge is the connection system between concrete slabs and steel truss members, several connection systems were proposed and experimentally evaluated. Also, the selected joint system was applied to the real bride design and construction. The researches were performed on the connection system, since it can affect the global behavior of this bridge such as flexural and fatigue behaviors as well as the local behavior around the connection region. The evaluation study showned that HTB applied to a curved bridge or a eccentric loading bridge, characteristic has a weak torsional capacity compared to an ordinary PSC box girder bridges due to the open structure of HTB. In this study, three box shaped hybrid truss specimens were made and the torsional test and evaluation for them were performed in order to find out the torsional behavior of HTB according to the connection system.
Mix Design Conditions at Early Curing Age of PCS-Coating Material Effected on Improvement in Bond Strength of Coated Rebar
Jo, Young-Kug ; Park, Dong-Yeol ; Kim, Wan-Ki ;
Journal of the Korea Concrete Institute, volume 25, issue 1, 2013, Pages 73~80
DOI : 10.4334/JKCI.2013.25.1.073
Polymer cement slurry (PCS) made from organic polymer dispersion and cement has good adhesion to steel, waterproofness and acid resistance due to being of polymer films formed in cement slurry. The purpose of this study is to evaluate the mix design conditions at early curing age of PCS-coating material effected on improvement in bond strength of coated rebar. The test pieces are prepared with two types of polymer dispersions such as St/BA and EVA, four polymer-cement ratios, two types of cement, four coating thicknesses and three curing ages, and tested for the bond strength test. From the test results, in general, bond strength of PCS-coated rebar is better than that of uncoated rebar and epoxy-coated rebar. It is also high bond strength at curing ages of 7-day or less, and coating thicknesses of
. The maximum bond strength of PCS-coated rebar at curing age of 3-hour is almost same as that of curing age of 1-day and 7-day. The maximum bond strength of PCS-coated rebar with ultra high-early strength cement and St/BA at polymer-cement ratio of 80%, and coating thickness of
is about 1.52 and 1.58 times respectively, the strength of uncoated rebar and epoxy-coated rebar. It is apparent that the curing age, coating thickness, type of polymer and cement are very important factors to improve the bond strength of PCS-coated rebar to cement concrete. We can have basic information that PCS-coated rebar with curing age at 3-hour and coating thickness of
can replace epoxy-coated rebar.
Evaluation of Design Method and Shear Transfer Capacity on the Horizontal Interface of PC Composite Beams
Moon, Jeong-Ho ; Oh, Young-Hun ;
Journal of the Korea Concrete Institute, volume 25, issue 1, 2013, Pages 81~90
DOI : 10.4334/JKCI.2013.25.1.081
The purpose of this study is to evaluate the horizontal shear strength on the interface between PC and cast-in-place concrete for PC composite beams. Six specimens were tested to examine the structural performance of the horizontal interface with different surface condition and stirrup detailing. Except for SF-291B specimen failed in flexural compression, strengths and deformation capacities of five specimens were determined by horizontal shear failure. Horizontal shear strengths by composite horizontal shear or shear friction in current codes could be used to predict the horizontal shear capacity of the interface for specimens. Also detailing for stirrup by PCI design provision could be used to accomplish the composite action in the interface.
Flexural Strength of PHC Pile Reinforced with Infilled Concrete, Transverse and Longitudinal Reinforcements
Bang, Jin-Wook ; Hyun, Jung-Hwan ; Lee, Bang-Yeon ; Lee, Seung-Soo ; Kim, Yun-Yong ;
Journal of the Korea Concrete Institute, volume 25, issue 1, 2013, Pages 91~98
DOI : 10.4334/JKCI.2013.25.1.091
The pre-tensioned spun high strength concrete (PHC) pile has poor load carrying capacity in shear and flexure, while showing excellent axial load bearing capacity. The purpose of this study is to evaluate the flexural performance of the concrete-infilled composite PHC (ICP) pile which is the PHC pile reinforced with infilled concrete, transverse and longitudinal reinforcement for the improvement of shear and flexural load carrying capacity. The ICP pile specimen was designed to make allowable axial compression and bending moment higher load bearing capacity than those determined through the investigation of abutment design cases. The allowable axial compression and bending moment of the ICP pile was obtained using the program developed for calculating the axial compression - bending moment interaction. Then, ICP pile specimens were manufactured and flexural tests were performed. From the test results, it was found that the maximum bending moment of the ICP pile was approximately 45% higher than that of the PHC pile and the safety factor of ICP pile design was about 4.5 when the allowable bending moment was determined to be 25% of the flexural strength.
A Study on the Penetration Resistance and Spalling Properties of High Strength Concrete by Impact of High Velocity Projectile
Kim, Hong-Seop ; Nam, Jeong-Soo ; Hwang, Heon-Kyu ; Jeon, Joong-Kyu ; Kim, Gyu-Yong ;
Journal of the Korea Concrete Institute, volume 25, issue 1, 2013, Pages 99~106
DOI : 10.4334/JKCI.2013.25.1.099
Concrete materials subjected to impact by high velocity projectiles exhibit responses that differ from those when they are under static loading. Projectiles generate localized effects characterized by penetration of front, spalling of rear and perforation as well as more widespread crack propagation. The magnitude of damage depends on a variety of factors such as material properties of the projectile, impact velocity, the mass and geometry as well as the material properties of concrete specimen size and thickness, reinforcement materials type and method of the concrete target. In this study, penetration depth of front, spalling thickness of rear and effect of spalling suppression of concrete by fiber reinforcement was evaluated according to compressive strength of concrete. As a result, it was similar to results of the modified NDRC formula and US ACE formula that the more compressive strength is increased, the penetration depth of front is suppressed. On the other hand, the increase in compressive strength of concrete does not affect spalling of rear suppression. Spalling of rear is controlled by the increase of flexural, tensile strength and deformation capacity.
Evaluation on the Impact Resistant Performance of Fiber Reinforced Concrete by High-Velocity Projectile and Contacted Explosion
Nam, Jeong-Soo ; Kim, Hong-Seop ; Lee, In-Cheol ; Miyauchi, Hiroyuki ; Kim, Gyu-Yong ;
Journal of the Korea Concrete Institute, volume 25, issue 1, 2013, Pages 107~114
DOI : 10.4334/JKCI.2013.25.1.107
In this study we experimentally evaluated an impact resistant performance of fiber reinforced concrete in the moment of explosion by high-velocity projectile with emulsion explosive. To assess the impact resistance, we conducted the impact test of high-velocity projectile which reaches an impact speed of 350 m/s and the experiment of contact exploding emulsion explosive. As a result, bending and tensile performance depending on type of PVA, PE fiber (polyvinyl alcohol fiber, polyethylene fiber) and steel fiber affects destruction of rear side in the form of spalling. Destroying the backside of the concrete compressive strength compared to suppress the bending and tensile performance is affected. In addition, the experiment shows that the destruction patterns of concrete specimen producted by high velocity impact and contact explosion are significantly similar. Therefore, it is possible to predict the destruction patterns of specimens in the situation of contact explosion by high-velocity projectile.
Engineering Performance and Applicability of Environmental Friendly Porous Concrete for a Marine Ranch Using Steel Industry By-products
Lee, Byung-Jae ; Jang, Young-Il ; Kim, Yun-Yong ;
Journal of the Korea Concrete Institute, volume 25, issue 1, 2013, Pages 115~123
DOI : 10.4334/JKCI.2013.25.1.115
The steel industry, a representative industry that significantly consumes raw materials and energy, produces steel as well as a large amount of by-product steel slag through the production process. The vast habitat foundation of marine life has been destroyed due to recent reckless marine development and environment pollution, resulting in intensification of the decline of marine resources, and a solution to this issue is imperative. In order to propose a method to recycle large amounts of by-product slag into a material that can serve as an alternative to natural aggregate, the engineering properties and applicability for each mixing factor of environment friendly porous concrete as a material for the composition of marine ranches were evaluated in this study. The test results for percentage of voids per mixing ratio revealed that the margin of error for all conditions was within 2.5%. The compressive strength test results showed that the most outstanding environmental friendly porous concrete can be manufactured when mixing 30% slag aggregate and 10% specially treated granular fertilizer for the optimum volume fraction. As concrete for marine applications, the best seawater resistance was obtained with mixing conditions for high compression strength. An assessment of the ability to provide a marine life habitat foundation of environmentally friendly porous concrete showed that a greater percentage of voids facilitated implantation and inhabitation of marine life, and the mixing of specially treated granular fertilizer led to active initial implantation and activation of inhabitation. The evaluation of harmfulness to marine life depending on the mixture of slag aggregate and specially treated granular fertilizer revealed that the stability of fish is secured.