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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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Study on the Critical Threshold Chloride Content for Steel Corrosion in Concrete with Various Cement Contents
Yang, Seung-Kyu ; Kim, Dong-Suck ; Um, Tai-Sun ; Lee, Jong-Ryul ; Kono, Katsuya ;
Journal of the Korea Concrete Institute, volume 20, issue 4, 2008, Pages 415~421
DOI : 10.4334/JKCI.2008.20.4.415
Reinforced concrete starts to corrode when the chloride ion concentration which is the sum of included in concrete and penetrated from environments exceeds a certain level of critical chloride concentration. Therefore each country regulates the upper bounds of chloride amount in concrete and the regulations are different for each country due to its circumstances. In this study, the critical threshold chloride content according to unit cement amount is empirically calculated to propose a reasonable regulation method on the chloride amount. As a result, the critical threshold chloride content increases considerably according to cement content and it agrees with the established theories. The present regulations on total chloride amount 0.3 or 0.6 kg chloride ions per
of concrete does not reflect the influences of mix design, environmental conditions and etc. So it can be said that it is more reasonable to regulate the critical threshold chloride content by the ratio of chloride amount per unit cement content than by the total chloride content in
Strengthen Effect of RC Beam Overlaid or Repaired by VES-LMC
Choi, Sung-Yong ; Yun, Kyong-Ku ; Choi, Seung-Sic ;
Journal of the Korea Concrete Institute, volume 20, issue 4, 2008, Pages 423~430
DOI : 10.4334/JKCI.2008.20.4.423
VES-LMC (very-early strength latex-modified concrete) has been widely used as repair material for bridge deck overlay or rehabilitation, because the overlaid or repaired could be opened to the traffic after 3 hours of curing. Although the field performance of VES-LMC generally indicates that it has an excellent bonding to the substrate and shows a long term performance, little quantitative data or research results have been presented in the literature on structural studies. The purpose of this study was to investigate the flexural behavior, interfacial performance, crack propagation, and strengthen effect of RC beam overlaid or repaired by VES-LMC through the 4-point flexural loading test. Two different types of RC beam were fabricated for repair and rehabilitation types. The test result showed that the strengthen effect, in term of flexural stiffness, increases as the depth of repair or overlay increases. More than 40% of stiffness was improved when the depth of repair was up to steel position. However, there was a little difference between 80 mm and 120 mm repaired beam. This means the repair depth must be considered. The interfacial behavior data showed that the repaired or overlaid beams had a little relative displacement. This means that two materials behave comparatively acting together. However, there were two specimens which had large displacement at the interface, because of poor bond strength. This suggested that interface treatment is one of the most important jobs in composite beams.
Expansion Behavior of Aggregate of Korea due to Alkali-Silica Reaction by ASTM C 1260 Method
Yun, Kyong-Ku ; Hong, Seung-Ho ; Han, Seung-Hwan ;
Journal of the Korea Concrete Institute, volume 20, issue 4, 2008, Pages 431~437
DOI : 10.4334/JKCI.2008.20.4.431
The concrete pavement at Seohae Expressway in Korea has suffered from serious distress, only after four to seven years of construction. The deterioration of ASR has seldom been reported per se in Korea, because the aggregate used for the cement concrete has been considered safe against alkali-silica reaction so far. The purpose of this study is to examine the expansion behavior of aggregates of Korea due to alkali-silica reaction by ASTM C 1260 standard method of the accelerated mortar bar test (AMBT), stereo microscopic analysis, scanning electronic microscope (SEM) analysis, and electron dispersive X-ray spectrometer (EDX) analysis. The results are presented as it follows. The accelerated mortar bar test (AMBT) showed that mica granite and felsite of igneous rocks, aroke, red sandstone and shale of sedimentary rocks, slate of metamorphic rock, and dendrite and quartz of mineral rock showed more expansion than 0.1% at 14 days. But, some sedimentary rocks and metamorphic rocks expanded more than 0.1% at 28 days even though they were less than 0.1% at 14 days. The mortar bars, which showed more than occurred 0.1% expansion, resulted in cracking on surface. SEM and EDX analysis confirmed that the white gel was a typical reaction product of ASR. The ASR gel in Korea mainly consisted of Silicate (Si) and Potassium (K) from the cement. The crack in the concrete pavement was caused by ASR. It seems that Korea is no longer safe zone against alkali-silica reaction.
Chloride Penetration Resistance of Ternary Blended Concrete and Discussion for Durability
Song, Ha-Won ; Lee, Chang-Hong ; Lee, Kewn-Chu ; Kim, Jae-Hwan ; Ann, Ki-Yong ;
Journal of the Korea Concrete Institute, volume 20, issue 4, 2008, Pages 439~449
DOI : 10.4334/JKCI.2008.20.4.439
Mineral admixtures are used to improve the quality of concrete and to develop sustainability of concrete structures. Supplementary cementitious materials (SCM), such as silica fume (SF), granulated blast furnace slag (GGBS) and pulverized fly ash (PFA), are gradually recognized as useful mineral admixture for producing high performance concrete. The study on ternary blended concrete utilizing mainly three major mineral admixtures is limited and the study on durability and chloride induced corrosion resistance of ternary blended concrete is very few. This study examines the durability characteristics of the ternary blended concrete composed of different amount of the SCM with ordinary Portland concrete and the study experimentally focuses on corrosion resistance evaluation of ternary blended concrete subjected to chloride attack. In this study, 50% replacement ratio of mineral admixture to OPC was used, while series of combination of
PFA binder were used for chloride corrosion resistance test. This study concerned the durability properties of the ternary blended concrete including the corrosion resistance, chloride binding, chloride transport and acid neutralization capacity. It was found that the ternary blended concrete utilizing the SCM densified the pore structures to lower the rate of chloride transport. Also, increased chloride binding and buffering to acid were observed for the ternary blended concrete with chlorides in cast.
Shake Table Response and Analysis of RC Bridge Piers with Lap-Spliced Steel under NFGM
Chung, Young-Soo ; Park, Chang-Young ; Hong, Hyun-Ki ; Park, Ji-Ho ; Shim, Chang-Su ;
Journal of the Korea Concrete Institute, volume 20, issue 4, 2008, Pages 451~458
DOI : 10.4334/JKCI.2008.20.4.451
The near-fault ground motion (NFGM) is characterized by a single long period velocity pulse of large magnitude. NFGM's have been observed in recent strong earthquakes, Izmit Turkey (1999), Kobe Japan (1995), Northridge USA (1994), etc. These strong earthquakes have caused considerable damage to infrastructures because the epicenter was close to the urban area, called as NFGM. Extensive research for the near-fault ground motion (NFGM) have been carried out in strong seismic region, but limited research have been done for NFGM in low or moderate seismic regions because of very few records. The purpose of this study is to investigate and analyze the effect of near-fault ground motions on reinforced concrete (RC) bridge piers with lap-spliced longitudinal reinforcing steels. The seismic performance of four RC bridge piers under near-fault ground motions was investigated on the shake table. In addition, a RC bridge pier is subjected to pseudo-dynamic loadings. Test results showed that large residual displacements were observed in RC bridge piers under NFGM. RC specimens on the shake table failed at relatively low displacement ductility, compared with the displacement ductility of RC bridge pier subjected to pseudo-dynamic loadings.
Analysis of Crack Width and Deflection Based on Nonlinear Bond Characteristics in Reinforced Concrete Flexural Members
Lee, Gi-Yeol ; Kim, Woo ;
Journal of the Korea Concrete Institute, volume 20, issue 4, 2008, Pages 459~467
DOI : 10.4334/JKCI.2008.20.4.459
This paper describes a proposal for average crack width and immediate deflection calculation in structural concrete members. The model is mathematically derived from actual bond stressslip relationships and tension stiffening effect between reinforcement and the surrounding concrete, and the actual strains of steel and concrete are integrated respectively along the embedded length between the adjacent cracks so as to obtain the difference in the axial elongation. With these, a model for average crack width and immediate deflection in reinforced concrete flexural members are proposed utilizing difference in the axial elongation and average steel strain and moment-curvature relationship with taking account of bond characteristics. The model is applied to the test specimens available in literatures, and the crack width and deflections predicted by the proposal equation in this study are closed to the experimentally measured data compared the current code provisions.
Characteristic of Microcracks with Mixing Proportional Properties of Concrete
Yoon, In-Seok ; Kim, Young-Geun ; Park, Ki-Bong ;
Journal of the Korea Concrete Institute, volume 20, issue 4, 2008, Pages 469~475
DOI : 10.4334/JKCI.2008.20.4.469
It is obvious that chloride penetration through cracks can threaten the durability of concrete substantially, according to the previous studies of author. It was proposed that crack depth corrseponded with critical crack width from the surface is a crucial factor in view of durability design of concrete structures. It is now necessary to deal with chloride penetration through microcracks characterized with the mixing features of concrete. The purpose of this study is examining the effect of mix proportional features of concrete such as coarse aggregate, high strengtherize of concrete and reinforcement of steel fiber on chloride penetration through cracks. Although small size of coarse aggregate can lead to many microcracks in concrete, the cracks should not impact on chloride penetration directly. On the contrary, chloride should penetrate through cracks easily in concrete with a large size of coarse aggregate because mixrocracks are connected to each other. Second, high strength concrete has an excellent performance to resist with chloride penetration. However, for cracked high strength concrete, its performance is reduced upto the level of ordinary concrete. Finally, steel fiber reinforcement is effective to reduce chloride penetration through cracks because steel fiber reinforcement can lead to reduce crack depth significantly.
Bond-Slip Model of Interface between CFRP Sheets and Concrete Beams Strengthened with CFRP
Kim, Sung-Bae ; Kim, Jang-Ho Tay ; Nam, Jin-Won ; Kang, Suk-Hwa ; Byun, Keun-Joo ;
Journal of the Korea Concrete Institute, volume 20, issue 4, 2008, Pages 477~486
DOI : 10.4334/JKCI.2008.20.4.477
External bonding of carbon fiber reinforced plastic sheets has recently emerged as a popular method for strengthening reinforced concrete structures. The behavior of CFRP-strengthened RC structure is often controlled by the behavior of the interface between CFRP sheets and concrete. In this study, a review of models on bond strength, bond-slip, and interfacial stresses has been first carried out. Then a new bond-slip model is proposed. The proposed bond-slip model has bilinear ascending regions and exponential descending region derived from modifications mode on the conventional bilinear bond-slip model. The comparison of the results with those of existing experiment researches on bond-slip models indicate good agreements.
Durability Evaluation of Tunnel Lining Concrete Reinforced with Nylon Fiber
Jeon, Joong-Kyu ; You, Jin-O ; Moon, Jae-Heum ;
Journal of the Korea Concrete Institute, volume 20, issue 4, 2008, Pages 487~493
DOI : 10.4334/JKCI.2008.20.4.487
Tunnel structures are widely used for transportations in mountains areas. To shorten the construction period and to cut down the construction expenditure, a construction technique that a tunnel excavation process and a tunnel lining process are simultaneously performed is often applied in the field. However, due to the vibration and impact caused by excavation process, cracking and deterioration of tunnel lining concrete could happen. This research experimentally investigated the effective role of the usages of blended cement and recently developed nylon fibers for tunnel lining concrete. It has been observed that both nylon fibers and blended cement improve the durability and physical properties of concrete.
Evaluation of Properties of Sulfur-Oxidizing Bacteria Growth and Resistance to Biochemical Corrosion by Simulation Test
Kim, Gyu-Yong ; Lee, Eui-Bae ; Khil, Bae-Su ; Lee, Seung-Hun ;
Journal of the Korea Concrete Institute, volume 20, issue 4, 2008, Pages 495~502
DOI : 10.4334/JKCI.2008.20.4.495
To analyze the growth of SOB(Thiobacillus novellus) and biochemical corrosion of concrete, simulation test method and device were developed, and basic conditions for SOB growth were established. Two types of simulation tests were conducted according to a transplant method and a concentration of
. As a result, the SOB growth in distinct manners and antibiosis of specimen were observed. In the case of the specimens indirectly transplanted with SOB through culture solution submersion at a hydrogen sulfide level of 120 ppm, the rapid activation of SOB and the resulting sulfuric acid production were observed. However, SOB were shown to grow rapidly and then die out in a relative short period of time. Meanwhile, in the case of the specimens directly transplanted with SOB at a hydrogen sulfide level of 50 ppm, the long-term growth of SOB was possible, but the production of sulfuric acid by SOB did not progress. In the case of the antibiotic metal-mixed specimens, SOB with destroyed cell membranes and internal organizations were observed.
Torsional Strength and Failure Modes of Reinforced Concrete Beams Subjected to Pure Torsion
Lee, Jung-Yoon ; Kim, Sang-Woo ; Kim, Ji-Hyun ;
Journal of the Korea Concrete Institute, volume 20, issue 4, 2008, Pages 503~511
DOI : 10.4334/JKCI.2008.20.4.503
This paper presents the results of an analytical and experimental study on the performance of reinforced concrete beams subjected to pure torsion. The main parameters of the experimental tests were amount of torsional reinforcement and the ratio of the transverse torsional reinforcement to the longitudinal torsional reinforcement. The test results indicated that the maximum amount of torsional reinforcement required in ACI 318-05 code underestimated almost twice as much as the observed maximum amount of torsional reinforcement. Comparisons between the tested and calculated torsional behaviors of the 102 beams showed that the torsional failure modes of ACI 318-05 code disagreed with the observed failure modes. In addition, the torsion provisions in ACI 318-05 code overestimate the torsional strength of the RC beams in which relatively large amount of torsional reinforcement were reinforced, while underestimate for the beams with small amount of torsional reinforcement. This discrepancy between the theoretical ultimate torsional strength as given by the ACI 318-05 code and the experimental one can be due to neglecting the tension stiffening effect and the contribution of the torsional strength by concrete.
Fiber Classification and Detection Technique Proposed for Applying on the PVA-ECC Sectional Image
Kim, Yun-Yong ; Lee, Bang-Yeon ; Kim, Jin-Keun ;
Journal of the Korea Concrete Institute, volume 20, issue 4, 2008, Pages 513~522
DOI : 10.4334/JKCI.2008.20.4.513
The fiber dispersion performance in fiber-reinforced cementitious composites is a crucial factor with respect to achieving desired mechanical performance. However, evaluation of the fiber dispersion performance in the composite PVA-ECC (Polyvinyl alcohol-Engineered Cementitious Composite) is extremely challenging because of the low contrast of PVA fibers with the cement-based matrix. In the present work, an enhanced fiber detection technique is developed and demonstrated. Using a fluorescence technique on the PVA-ECC, PVA fibers are observed as green dots in the cross-section of the composite. After capturing the fluorescence image with a Charged Couple Device (CCD) camera through a microscope. The fibers are more accurately detected by employing a series of process based on a categorization, watershed segmentation, and morphological reconstruction.
The Failure Model of RC Flat Plates Considering Interrelation between Punching Shear and Unbalanced Moment
Choi, Jung-Wook ; Song, Jin-Kyu ; Song, Ho-Beom ;
Journal of the Korea Concrete Institute, volume 20, issue 4, 2008, Pages 523~530
DOI : 10.4334/JKCI.2008.20.4.523
In structural design provision, maximum punching shear stress of slabs is prescribed as combined stress in direct shear occurred by gravity load and eccentric shear occurred by unbalanced moment. This means that the effect of unbalanced moment is considered to decide the punching shear stress. However, from the resistance capacity standpoint, the effect of unbalanced moment strength is not considered for deciding punching shear strength. In this paper, a model considering interrelation between unbalanced moment and punching shear was proposed. In the model, the relation between load effect and resistance capacity in unbalanced moment and punching shear was two-dimensionally expressed. Using the interrelation model, a method how unbalanced moment strength should be considered to decide the punching shear strength was proposed. Additionally, effective width enlargement factors for deciding the unbalanced moment strength of flat plates with shear reinforcements were proposed. The interrelation model proposed in this paper is very effective for the prediction of the behavior of slab-column connection because not only punching shear and unbalanced moment strengths but also failure modes of flat plates can be accurately predicted.
Evaluation of Flexural Strength for Normal and High Strength Concrete with Hooked Steel Fibers
Oh, Young-Hun ;
Journal of the Korea Concrete Institute, volume 20, issue 4, 2008, Pages 531~539
DOI : 10.4334/JKCI.2008.20.4.531
The purpose of this study is to investigate the mechanical properties of high strength concretes reinforced with hooked steel fiber. For this purpose, total 36 specimens whose variables are concrete compressive strength, steel fiber aspect ratio, and steel fiber volume contents, are made and tested. From the test results including previous research work, flexural performance of steel fiber reinforced high strength concrete is evaluated in terms of flexural strength and toughness index. Flexural behavior of steel fiber reinforced high strength concrete is enhanced with respect to the fiber volume content, the aspect ratio, and concrete compressive strength. More efforts are devoted to evaluate quantitatively between the flexural strength and the structural parameters such as the fiber volume content, the aspect ratio, and concrete compressive strength.