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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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Journal DOI :
Korea Concrete Institute
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Volume & Issues
Volume 23, Issue 6 - Dec 2011
Volume 23, Issue 5 - Oct 2011
Volume 23, Issue 4 - Aug 2011
Volume 23, Issue 3 - Jun 2011
Volume 23, Issue 2 - Apr 2011
Volume 23, Issue 1 - Feb 2011
Selecting the target year
An Experimental Study on the Performance of Bond-Type Anchorage Systems with Various Dimensions of Steel Mold
Jung, Woo-Tai ; Park, Young-Hwan ; Park, Jong-Sup ;
Journal of the Korea Concrete Institute, volume 23, issue 3, 2011, Pages 257~264
DOI : 10.4334/JKCI.2011.23.3.257
This paper contains the experimental performance evaluation results of bond-type anchorage systems with the CFRP(carbon fiber reinforced polymer) tendon. The preliminary tests were performed to find the appropriate filling materials in the steel molds. A total of five materials including epoxy or cement mortar have been used as fillers in the steel molds. Results of the preliminary tests showed that specimen filled with non-shrinkage mortar showed maximum tensile strength. Based on the finding, the non-shrinkage mortar was selected as filler for anchoring CFRP tendons. Additional tests were performed as a parametric study to select proper size of steel molds such as external diameter, thickness, and length. The proper size of steel molds with non-shrinkage mortar was selected based on the test results, which gave stable tensile performance.
Surface Properties of Color Concrete Using Acid Stained Agent
Kim, Jin-Man ; Jeong, Ji-Yong ; Park, Hyo-Jin ;
Journal of the Korea Concrete Institute, volume 23, issue 3, 2011, Pages 265~272
DOI : 10.4334/JKCI.2011.23.3.265
Even though concrete is the most important material for building structures, its intrinsic gray color degrades urban esthetics. In order to improve this problem, coloring methods of mixing pigment in concrete batch and painting the surface of concrete surface have been tried. However, applications of the coloring methods in construction field are difficult due to high cost and low durability. Recently, acid stain agent is emerging as a new coloring method for concrete. It is able to apply a remarkably thin colored layer on a concrete surface from chemical reaction between acid and alkaline solutions. This study has examined the changes and variations of the surface layer of mortar specimen from chemical reaction of acid stained agents. The colors were changed into natural irregular stains according to aging. After the staining, no shape change was found from visible inspections. Microstructure of the colored surface applied with acid stained agent was much rougher than that of original mortar. When the colored layer was compared to original surface, crystals of hydrate such as
and C-S-H gel were observed. Surface hardness was same or slightly higher in the colored layer. The value of pH was reduced by approximately 10%, weight contents of elements such as Ca, Si, and Al were low. In the chemical composition of the colored layer, the non-cement based elements of Mn, Cr, and Cu increased. Also, Fe and alkali elements of K and Na increased.
Flexural Behavior of FRP Bar Reinforced HSC Beams with Different Types of Reinforcing Bar and Fiber
Yang, Jun-Mo ; Shin, Hyun-Oh ; Min, Kyung-Hwan ; Yoon, Young-Soo ;
Journal of the Korea Concrete Institute, volume 23, issue 3, 2011, Pages 273~280
DOI : 10.4334/JKCI.2011.23.3.273
Ten high-strength concrete beam specimens, which have various combinations of different types of flexural reinforcement and short fibers were constructed and tested. Six beams were reinforced with two layers of steel, CFRP, and GFRP bar combinations. The other four beams were reinforced with two layers of single type CFRP and GFRP bars, with steel and synthetic short fibers. An investigation was performed on the influence of the parameters on the load-carrying capacity, post cracking stiffness, cracking pattern, deflection behavior, and ductility. The low post cracking stiffness, large deflection, deep crack propagation, large crack width, and low ductility of FRP bar-reinforced beams were controlled and improved by positioning steel bars in the inner layer of the FRP bar layer. In addition, the addition of fibers increased the first-cracking load, ultimate flexural strength, and ductility as well as the deep propagating cracks were controlled in the FRP bar-reinforced concrete beams. The increased ultimate concrete strain of fiber-reinforced concrete should be determined and considered when FRP bar-reinforced concrete members with fibers are designed.
A Study on Behavior Characteristics of Precast Coping Part under Axial Load
Won, Deok-Hee ; Lee, Dong-Jun ; Kim, Seung-Jun ; Kang, Young-Jong ;
Journal of the Korea Concrete Institute, volume 23, issue 3, 2011, Pages 281~287
DOI : 10.4334/JKCI.2011.23.3.281
Recently, bridge construction technology has made great progress from development of high performance materials and new bridge types. However, most technology are based on methods of cast-in-place and material cost saving. The method of cast-in-place concrete causes environmental damages and costumer complaints. Especially, under bad weather conditions, the construction can not proceed. To overcome these disadvantages, new construction methods were developed to reduce construction time. These methods are called precast method. Most prefabricated methods have been applied to superstructure constructions of bridges, but very minutely applied to substructure constructions. The most important agendas on precast method are light weight and transportability of the precasted members, because very strict transporting specifications exist for road transportation of the precasted members. For example, the weight and length of coping members may be larger than the available transporting vehicles. Although column is constructed by precast method to save construction time, if coping member is constructed by cast-in-place method, then the column construction time reduction becomes meaningless. Therefore, in this study, a new precast coping member and a connecting system of column-coping member are proposed. The proposed method is verified by analyzing their ultimate performance through analysis and experimental study.
Quantitative Estimation of Joint Spacing for Concrete Slab to Prevent Cracking of Drying Shrinkage
Lee, Su-Jin ; Lee, Hoi-Keun ; Lee, Seung-Hoon ; Won, Jong-Pil ;
Journal of the Korea Concrete Institute, volume 23, issue 3, 2011, Pages 289~294
DOI : 10.4334/JKCI.2011.23.3.289
The installation of joint is to prevent random cracking due to drying shrinkage stress of concrete slab. However contraction joint spacing is empirically implemented into slab constructions without detail calculation based on quantitative criteria. In this study, shrinkage strain of concrete due to concrete shrinkage stress was measured to suggest joint spacing based on the study results. The test environmental conditions were applied temperature of
and relative humidity of 60%. The design compressive strength used was 30 MPa and 40 MPa, which are currently used in concrete slab designs. The drying shrinkage test result was applied to drying shrinkage models (ACI 209R, CEB MC 90, B3, GL 2000 and Sakata). The results showed that the most appropriate model was ACI 209R model. Based on the research findings, quantitative contraction joint spacing locations were calculated.
Autogeneous Shrinkage Characteristics of Ultra High Performance Concrete
Kim, Sung-Wook ; Choi, Sung ; Lee, Kwang-Myong ; Park, Jung-Jun ;
Journal of the Korea Concrete Institute, volume 23, issue 3, 2011, Pages 295~301
DOI : 10.4334/JKCI.2011.23.3.295
Recently, the use of UHPC made of superplasticizers, silica fume, and steel fibers has been increasing worldwide. Although UHPC has a very high strength as well as an excellent durability performance due to its dense microstructures, earlyage cracks may occur due to the high heat of hydration and autogenous shrinkage caused by low W/B and high unit cement content. The early-age shrinkage cracking of UHPC can be controlled by using the shrinkage reducers and expansive admixtures having autogenous shrinkage compensation effect. In this paper, ultrasonic pulse velocity of UHPC containing shrinkage reducers and expansive agents was measured to predict its stiffness change. Also, the effect of shrinkage reducers and expansive agents on the autogenous shinkage of UHPC was investigated through the shrinkage test of UHPC specimens. Furthermore, the material coefficients of autogenous shrinkage prediction model were determined using the autogenous shrinkage values of UHPC with age. Consequently, the test results showed that, by adding shrinkage reducers and expansive agents, the stiffness of UHPC was rapidly developed at early-ages and the autogenous shrinkage was considerably reduced.
Fatigue Capacity Evaluation of Hinge Type Connection System for a Hybrid Truss Bridge
Jung, Kwang-Hoe ; Yi, Jong-Won ; Lee, Sang-Hyu ; Kim, Jay Jang-Ho ;
Journal of the Korea Concrete Institute, volume 23, issue 3, 2011, Pages 303~310
DOI : 10.4334/JKCI.2011.23.3.303
To replace a steel box bridge for constructions of medium span bridges in Korea, the Hybrid Truss Bridge (HTB) is being considered as an alternative bridge type. The core technology of HTB is the connection joint that links the concrete slabs and steel truss pipes. Various construction companies in Japan have developed unique connection systems and applied to the real bridge constructions after verifying their performances through the experimental evaluation. In this study, the fatigue test of a hybrid truss girder has been performed in order to verify the newly proposed hinge type connection joint`s static and fatigue capacities. Through this fatigue test results, it is founded that the structural detail to improve the fatigue capacity should be developed. The hinge connection system with circular ribs has been proposed by means of structural finite element analyses. And then the fatigue test for this connection joint has been performed and it is proved that this connection joint has enough fatigue capacity. Finally, it is expected that the hinge connection system with circular ribs developed by in this study can be easily applied to the real bridge.
Evaluation for Properties of Domestic Pond Ash Aggregate and Durability Performance in Pond Ash Concrete
Lee, Bong-Chun ; Jung, Sang-Hwa ; Kim, Joo-Hyung ; Kwon, Seung-Jun ;
Journal of the Korea Concrete Institute, volume 23, issue 3, 2011, Pages 311~320
DOI : 10.4334/JKCI.2011.23.3.311
Fly ash (FA), byproduct from power plant has been actively used as mineral admixture for concrete. However, since bottom ash (BA) is usually used for land reclaim or subbase material, more active reuse plan is needed. Pond ash (PA) obtained from reclaimed land is mixed with both FA and BA. In this study, 6 PA from different domestic power plant are prepared and 5 different replacement ratios (10%, 20%, 30%, 50%, and 70%) for fine aggregate substitutes are considered to evaluate engineering properties of PA as fine aggregate and durability performance of PA concrete. Tests for fine aggregate of PA for fineness modulus, density and absorption, soundness, chloride and toxicity content, and alkali aggregate reaction are performed. For PA concrete, durability tests for compressive strength, drying shrinkage, chloride penetration/diffusion, accelerated carbonation, and freezing/thawing are performed. Also, basic tests for fresh concrete like slump and air content are performed. Although PA has lower density and higher absorption, its potential as a replacement material for fine aggregate is promising. PA concrete shows a reasonable durability performance with higher strength with higher replacement ratio. Finally, best PA among 6 samples is selected through quantitative classification, and limitation of PA concrete application is understood based on the test results. Various tests for engineering properties of PA and PA concrete are discussed in this paper to evaluate its application to concrete structure.
A Study on the Residual Mechanical Properties of Fiber Reinforced Concrete with High Temperature and Load
Kim, Young-Sun ; Lee, Tae-Gyu ; Nam, Jeong-Soo ; Park, Gyu-Yeon ; Kim, Gyu-Yong ;
Journal of the Korea Concrete Institute, volume 23, issue 3, 2011, Pages 321~330
DOI : 10.4334/JKCI.2011.23.3.321
Recently, the effects of high temperature and fiber content on the residual mechnical properties of high-strength concrete were experimentally investigated. In this paper, residual mechanical properties of concrete with water to cement (w/c) ratios of 0.55, 0.42 and 0.35 exposed to high temperature are compared with those obtained in fiber reinforced concrete with similar characteristics ranging from 0.05% to 0.20% polypropylene (PP) fiber volume percentage. Also, factors including pre-load levels of 20% and 40% of the maximum load at room temperature are considered. Outbreak time, thermal strain, length change, and mass loss were tested to determine compressive strength, modulus of elasticity, and energy absorption capacity. From the results, in order to prevent the explosive spalling of 50 MPa grade concretes exposed to high temperature, more than 0.05 vol. % of PP fibers is needed. Also, the cross-sectional area of PP fiber can influence the residual mechanical properties and spalling tendency of fiber reinforced concrete exposed to high temperature. Especially, the external loading increases not only the residual mechanical properties of concrete but also the risk of spalling and brittle failure tendency.
An Experimental Study on Water-Purification Properties in Cement Bricks Using Effective Micro-Organisms and Zeolite
Kim, Wha-Jung ; Choi, Kil-Jun ; Park, Jun-Seok ;
Journal of the Korea Concrete Institute, volume 23, issue 3, 2011, Pages 331~338
DOI : 10.4334/JKCI.2011.23.3.331
The purpose of this study is to use organisms or micro-organism functions for eco-friendly water-purification of cement bricks, utilizing bioremediation. Many researches have been performed in the past to improve water quality by using effective micro-organisms in construction materials. In order to purify water using micro-organisms, this research used soybean paste bacteria, an effective micro-organism that was identified through 16S rDNA sequence analysis performed in Daegu S. Environment Protection Institute in addition to Natto bacteria that was studied in the previous research. With these effective micro-organisms with water-purification ability, this study examined their water-purification possibility on cement bricks. This study used Zeolite to immobilize micro-organisms to bricks, and confirmed that the micro-organisms were attached on Zeolite from SEM analysis. The experimental results showed that specific micro-organisms can be used to effectively remove contamination an used to develop eco-friendly construction materials. The study on micro-organisms for material purification shows great promises as a future research topic.
Effect of Mineral Admixture on Bond Properties between Polyolefin Based Synthetic Fiber and Cement Mortar
Lee, Jin-Hyeong ; Park, Chan-Gi ;
Journal of the Korea Concrete Institute, volume 23, issue 3, 2011, Pages 339~346
DOI : 10.4334/JKCI.2011.23.3.339
The effects of mineral admixtures on the bonding properties of cement mortar to polyolefin based synthetic fiber were evaluated. The mineral admixtures consisted of 0%, 5%, 10%, and 15% fly ash, blast furnace slag, and metakaolin in cement. Bond interactions between the cement mortar and the polyolefin based synthetic fiber were determined by Dog-bone bond tests. Bond tests of the polyolefin based synthetic fiber showed an increase in pullout load with the strength of the cement mortar. Also, the interface toughness of polyolefin based synthetic fiber in cement mortar increased as the fly ash, blast furnace slag, and metakaolin contents increased. The microstructure of polyolefin based synthetic fiber surface was examined after the pullout test to analyze the frictional resistant force according to the replacement ratio of fly ash, blast furnace slag, and metakaolin during the pullout process of polyolefin based synthetic fiber in cement mortar. The scratched of polyolefin based synthetic fibers increased with the replacement ratio of fly ash, blast furnace slag, and metakaolin. Also, the interface toughness was enhanced by adhesion forces induced by the fly ash, blast furnace slag, and metakaolin.
A Study on Setting Time and Early Strength of Tablet-Shaped Accelerators
Ryou, Jae-Suk ; Lee, Yong-Soo ;
Journal of the Korea Concrete Institute, volume 23, issue 3, 2011, Pages 347~352
DOI : 10.4334/JKCI.2011.23.3.347
When concrete is worked in cold weather, the methods of using hot air, water and aggregate heating, accelerators are used to prevent early frosting and to improve early strength. But these methods raise problems such as implementation difficulty, high cost, and energy losses. Among the available cold weathering methods, accelerator method is the most economical but with the drawbacks of rapid setting and insufficient workability in the initial hydration stage. Therefore, the tablet method usually used for pharmaceutical field was applied to the accelerator method to compare the controlled reaction time of the new and old accelerator method. Based on the test results, physical and mechanical properties of concrete were tested and the possibility of delaying initial reactions to increase the total reaction time was evaluated. The results showed that when both accelerators and tablet were used, setting-time decreased. Physical properties of concrete were optimal for tablet 0.5% and 1.0%. Also, accelerator 0.5%, tablet 0.5% and 1.0% showed good early strengths.
Allowable Compressive Stress of Pre-Tensioned Members with Tee or Inverted Tee Sections at Transfer
Lee, Deuck-Hang ; Lee, Jeong-Yeon ; Lim, Joo-Hyuk ; Kim, Kang-Su ;
Journal of the Korea Concrete Institute, volume 23, issue 3, 2011, Pages 353~364
DOI : 10.4334/JKCI.2011.23.3.353
In a previous research performed by the authors, the allowable compressive stress coefficient (K) in pretensioned members with rectangular section at transfer was proposed based on strength design theory. In this study, a subsequent research of an enormous analysis was performed to determine the K factor for Tee and inverted Tee section members, considering the effect of section height (h), section type, amount of tendons (
), and eccentricity ratio (e/h). Based on the analysis results, the allowable compressive stress coefficients (K) for Tee and inverted Tee section members at transfer were derived, which limit the maximum allowable stresses as 80% and 70% of the compressive strengths at the time of release for Tee section and inverted Tee section, respectively. And these were larger than the allowable stresses specified in domestic and other international codes. In order to verify the proposed equations, they were compared to the test results available in literature and other codes, which showed that the allowable stresses in domestic and international codes are unconservative for the cases with low eccentricity ratios while conservative for those with high eccentricity ratios. The proposed equations, however, estimate the allowable stresses of the Tee and inverted Tee section members reasonably close to test results.
Compressive Stress Distribution of Concrete for Performance-Based Design Code
Lee, Jae-Hoon ; Lim, Kang-Sup ; Hwang, Do-Kyu ;
Journal of the Korea Concrete Institute, volume 23, issue 3, 2011, Pages 365~376
DOI : 10.4334/JKCI.2011.23.3.365
The current Concrete Structural Design Code (2007) prescribe the equivalent rectangular stress block of the ACI 318 Building Code as concrete compressive stress distribution for design of concrete structures. The rectangular stress block may be enough for flexural strength calculation, but realistic stress-strain relationship is required for performance verification at selected limit state in performance-based design. Moreover, the ACI rectangular stress block provides non-conservative flexural strength for high strength concrete columns. Therefore a new stress distribution model is required for development of performance-based design code. This paper proposes a concrete compressive stress-strain distribution model for design and performance verification. The proposed model has a parabolic-rectangular shape, which is adopted by Eurocode 2 and Japanese Code (JSCE). It was developed by investigation of experimental test results conducted by the authors and other researchers. The test results cover high strength concrete as well as normal strength concrete. The stress distribution parameters of the proposed models are compared to those of the ACI 318 Building Code, Eurocode 2, Japanese Code (JSCE) and Canadian Code (CSA) as well as the test results.
Experimental Studies on the Effect of Various Design Parameters on Thermal Behaviors of High Strength Concrete Columns under High Temperatures
Shin, Yeong-Soo ; Park, Jee-Eun ; Mun, Ji-Young ; Kim, Hee-Sun ;
Journal of the Korea Concrete Institute, volume 23, issue 3, 2011, Pages 377~384
DOI : 10.4334/JKCI.2011.23.3.377
Although concrete is considered as fire proof materials, high strength concrete shows severe material and structural damages when exposed to fire. To understand such damages in high strength concrete structures, the effects of various design parameters and fire condition on the thermal behaviors of high strength concrete structures are investigated in this study. In order to achieve this goal, fire tests are performed on high strength concrete columns with different fire conditions and design parameters including cross sectional area, cover thickness, and reinforcement alignment. To investigate thermal behaviors, temperature distributions and amount of spalling are measured. In overall, the columns show rapidly increasing inner temperatures between 30~60 mins of the fire tests due to spalling. In detail, the higher temperature distributions are observed from the columns with the larger cross section and less cover thickness. Moreover, among the columns with same reinforcing ratio, larger number of reinforcements with the smaller diameter causes the higher temperature distribution. The findings from the experimental study allow not only understanding of thermal behaviors of high strength concrete columns under fire, but also guidance in revising fire safety design.
Improvement and Evaluation of Seismic Performance for Reinforced Concrete Beam-Column Joints Using High Performance Embedded FRP
Ha, Gee-Joo ; Shin, Jong-Hack ; Kang, Hyun-Wook ;
Journal of the Korea Concrete Institute, volume 23, issue 3, 2011, Pages 385~392
DOI : 10.4334/JKCI.2011.23.3.385
In this study, experimental research was carried out to evaluate and improve the seismic performance of reinforced concrete beam-column joint regions using strengthening materials (steel plate, carbon fiber sheet, and embedded carbon fiber rod) in existing reinforced concrete buildings. Six specimens of retrofitted beam-column joints are constructed using various retrofitting materials and tested for their retrofit performances. Specimens designed by retrofitting the beam-column joint regions (LBCJ series) of existing reinforced concrete building showed a stable mode of failure and an increase in load-carrying capacity due to the effect of crack control at the time of initial loading and confinement from retrofitting materials during testing. Specimens of LBCJ series, designed by the retrofitting of FRP in reinforecd beam-column joint regions increased its maximum load carrying capacity by 26~50% and its energy dissipation capacity by 13.0~14.4% when compared to standard specimen of LBCJC with a displacement ductility of 4.
Bond Strength Evaluation of RC Beams on the Rib Shape of Reinforcing Bars
Hong, Geon-Ho ; Kim, Jin-Ah ; Choi, Oan-Chul ;
Journal of the Korea Concrete Institute, volume 23, issue 3, 2011, Pages 393~400
DOI : 10.4334/JKCI.2011.23.3.393
The needs for high strength structural materials have recently increased, because construction and cost efficiencies are demanded by the costumers. But, the use of high strength reinforcing bars requires longer development and splice lengths compared to normal strength bars. This restriction may cause reduction in construction efficiency and require more complicated details. The purpose of this paper is to evaluate the bond strength on the rib shape of reinforcing bars to decrease development and splice lengths of high strength reinforcements. Total of 5 simple beam specimens were tested, and the main test variable was a rib shape of reinforcing bars. Test data was analyzed in the viewpoint of bond strength, load-deflection relationship, and crack pattern. Test results indicated that the bond strength of high relative rib area reinforcing bars increased up to 11% compared to normal strength reinforcements. And the improved rib shape reinforcements, which were formed with high and low height rib, increased the bond strength up to 23% even though the relative rib area was same as the high relative rib area reinforcements. Serviceability performances such as deflection number of cracking, and maximum crack width were similar in all specimens, so it is safe to conclude that the improved rib shape reinforcements can be applied to the structural members.