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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 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
Selecting the target year
Flexural Behaviors of GFRP Rebars Reinforced Concrete Beam under Accelerated Aging Environments
Park, Yeon-Ho ; Choi, Yeol ;
Journal of the Korea Concrete Institute, volume 25, issue 2, 2013, Pages 137~144
DOI : 10.4334/JKCI.2013.25.2.137
The use of fiber-reinforced polymer (FRP) reinforcing bars in concrete structures has been increased as an alternative of steel reinforcement which has shown greater vulnerability to corrosion problem. However, the long-term performance of concrete members with FRP reinforcement is still questioned in comparison to the used of steel reinforcement. This study presents the results of an experimental study on the long-term behaviors of GFRP (glass fiber reinforced polymer) bar reinforced concrete beams after exposed to accelerated aging in an environmental chamber with temperature of
) and 80% of relative humidity up to 300 days. The objectives of this research was to compare strength degradation and change of ductility between GFRP reinforced concrete beams and steel reinforcement beams after accelerated aging. Two types (wrapped and sand-coated surface) of GFRP bars and steel were reinforced. in concrete beams. Test results show that the failure modes of GFRP bar reinforced concrete beams are very similar with traditional RC beams, and the change of load-carrying capacity of steel reinforcing concrete beam is greater than that of GFRP bar reinforcing concrete beam under the accelerated aging. Test result also shows that the use of GFRP reinforcing in concrete could be introduced more brittle failure than that of steel reinforcing for practical application. The deformability factor up to compression failures indicates no significant variation before and after exposure of accelerated aging.
Analysis Technique for Chloride Penetration in High Performance Concrete Behavior Considering Time-Dependent Accelerated Chloride Diffusivity
Kwon, Seung-Jun ; Park, Sun-Gyu ;
Journal of the Korea Concrete Institute, volume 25, issue 2, 2013, Pages 145~153
DOI : 10.4334/JKCI.2013.25.2.145
Recently, accelerated chloride diffusion coefficients are used for an evaluation of chloride behavior. Similar as apparent diffusion coefficients, accelerated diffusion coefficients decrease with time. In this study, decrease in diffusion coefficient with time is simulated with porosity. Utilizing DUCOM-program, porosities from 15 mix proportions are obtained and diffusion coefficients are modelled with regression analysis of porosity for 270 days. Considering non-linear binding capacity which means the relation between free and bound chloride ion, chloride behavior in high performance concrete is evaluated. Through utilizing the previous test results for concrete under chlorides for 180 days, the applicability of the proposed technique is verified. The proposed technique is evaluated to reasonably predict the chloride behavior in concrete with various w/c (water to cement) ratios and mineral admixtures (GGBFS and FA). It is also shown that decrease in chloride diffusion should be considered for chloride prediction in concrete with mineral admixture since it has very clear decrease in diffusivity with time.
An Experimental Study for Bond Characteristics of Deformed Bar Embedded in Donut Type Biaxial Hollow Slab
Chung, Joo-Hong ; Kang, Sung-Hoon ; Lee, Seung-Chang ; Choi, Chang-Sik ; Choi, Hyun-Ki ;
Journal of the Korea Concrete Institute, volume 25, issue 2, 2013, Pages 155~163
DOI : 10.4334/JKCI.2013.25.2.155
This study investigated the bond characteristics of embedded deformed steel bar in donut type biaxial hollow slabs. The donut type hollow sphere make concrete inner cover formed between steel bar and hollow sphere due to the hollow shape and arrangement. Generally, inner cover was thinner than outer cover, and some part of donut type biaxial hollow slab has smaller inner cover thickness than
. It was affected to the bond condition of deformed bar. Furthermore, inner cover thickness changes along the longitudinal deformed bar due to hollow shape. Therefore, donut type hollow slab was divided 3 regions according to the hollow shape such as insufficient region, transition region, sufficient region. Pull-out test were performed to find out the effect of bond condition by the region. Main parameters are inner cover thickness, embedded length and bond location. Bond characteristics of donut type biaxial hollow slab were confirmed through comparison of bond stress-slip relationship, maximum bond strength and bond stress distribution of each regions. And the calculation method of bond strength of donut type biaxial hollow slab was suggested based on the test results.
Analytical and Experimental Studies on Splice Sleeves for SD500 Rebars
Oh, Young-Hun ; Moon, Jeong-Ho ;
Journal of the Korea Concrete Institute, volume 25, issue 2, 2013, Pages 165~173
DOI : 10.4334/JKCI.2013.25.2.165
Splice sleeves for HD25 and HD32 rebars with yield strength 500 MPa were studied experimentally and analytically. The shapes of sleeve was examined with nonlinear finite element analyses. A total of 18 specimens were tested with test variables of rebar types, sleeve lengths, mortar compressive strengths, and rebar development lengths. Three identical specimens per each variable were tested in order to prevent any test errors. After tests, numerical studies with a nonlinear finite element method were conducted to evaluate the test results. Experimental studies with 18 specimens showed that the sleeves of this study satisfies the code requirement. It was found that the strength of mortar and the bar development length within the sleeves did not affect to the load-carrying capacity of sleeves.
Shear Strength of Hybrid Beams Combining Precast Concrete and Cast-In-Place Concrete
Kim, Chul-Goo ; Park, Hong-Gun ; Hong, Geon-Ho ; Kang, Su-Min ;
Journal of the Korea Concrete Institute, volume 25, issue 2, 2013, Pages 175~185
DOI : 10.4334/JKCI.2013.25.2.175
Currently in precast concrete construction, precast concrete and cast-in-place concrete with different concrete strengths are used. However, current design codes do not provide shear design methods for PC-CIP hybrid members using dual concrete strengths. In the present study, the shear strengths of beams using dual concrete compressive strengths (24 MPa, 60 MPa) were tested. The test variables were the area ratio of the two concretes, longitudinal bar ratio, and shear span-to-depth ratio. The shear strengths of test specimens were evaluated by current design methods, using an effective concrete strength (considering the area ratio of the two concrete strengths). The test result showed that when 60 MPa concrete was used in the compressive zone and the longitudinal bar ratio was low, the shear strengths of the test specimens were less than the predictions. On the basis of the results, design recommendations were provided for the shear design of the PC-CIP hybrid beams.
Creep Behavior of Pultruded Ribbed GFRP Rebar and GFRP Reinforced Concrete Member
You, Young-Jun ; Park, Young-Hwan ; Kim, Hyung-Yeol ; Choi, Jin-Won ; Kim, Jang-Ho Jay ;
Journal of the Korea Concrete Institute, volume 25, issue 2, 2013, Pages 187~194
DOI : 10.4334/JKCI.2013.25.2.187
Fiber reinforced polymer (FRP) has been gathering interest from designers and engineers for its possible usage as a replacement reinforcement of a steel reinforcing bar due to its advantageous characteristics such as high tensile strength, non-corrosive material, etc. Since it is manufactured with various contents ratios, fiber types, and shapes without any general specification, test results for concrete members reinforced with these FRP reinforcing bars could not be systematically used. Moreover, since investigations for FRP reinforced members have mainly focused on short-term behavior, the purpose of this study is to evaluate long-term behaviors of glass FRP (GFRP) reinforcing bar and concrete beams reinforced with GFRP. In this paper, test results of tensile and bond performance of GFRP reinforcing bar and creep behavior are presented. In the creep tests, results showed that 100 years of service time can be secured when sustained load level is below 55% of tensile strength of GFRP reinforcing bar. A modification factor of 0.73 used to calculate long-term deflection of GFRP reinforced beams was acquired from the creep tests for GFRP reinforced concrete beams. It is expected that these test results would give more useful information for design of FRP reinforced members.
Control of Thermal Crack in Mass Concrete Using Automated Curing System
Ha, Ju-Hyung ; Cho, Yun-Gu ; Hyun, Tae-Yang ; Lim, Chang-Keun ; Seo, Tae-Seok ;
Journal of the Korea Concrete Institute, volume 25, issue 2, 2013, Pages 195~200
DOI : 10.4334/JKCI.2013.25.2.195
New thermal crack control system for mass concrete was developed to increase quality and to save construction period and cost. The principle of this system is that the curing water having proper temperature is supplied automatically to the surface of mass concrete member to keep the temperature difference between center and surface of concrete less than generally recommended temperature difference (
). Mock-up test was conducted to investigate the validity of newly developed curing system. As a result, no crack was founded in the specimen using automated curing system developed in this study, while many cracks occurred in another specimen without automated curing system. It was also confirmed that the strength and the durability of the concrete cured by automated curing system were improved.
A Study on Properties of Retarder via Tabletting Method
Ryou, Jae-Suk ; Yang, Neung-Won ; Lee, Yong-Soo ;
Journal of the Korea Concrete Institute, volume 25, issue 2, 2013, Pages 201~207
DOI : 10.4334/JKCI.2013.25.2.201
When hot weather concrete is utilized, the cooling methods of cooling pipe, liquid nitrogen, ice, etc., are used to prevent the poor consistency and cold joint due to high temperature. These methods, however, spike the production cost and energy consumption, and make quality control difficult. Among these methods is one that involves the use of a retarder. Although economical, retarder is caused difficulty of retarded hardening and setting time control due to inaccurate weighing and poor working condition. Therefore, how to make a tablet for hot weather concrete, as with the existing pharmacy and foods, is discussed in this study, including the following items: mortar setting time, flow test by elapsed time, physical and mechanical properties of concrete. As a result, gluconic acid is superior to lignosulfonic acid and the possibility of using them for such purpose without quality degradation was confirmed in this study, when retarder is tabletting.
Study on Physical and Chemical Properties of CaO-Al
System Melting Compound
Lee, Keun-Jae ; Koo, Ja-Sul ; Kim, Jin-Man ; Oh, Sang-Yoon ;
Journal of the Korea Concrete Institute, volume 25, issue 2, 2013, Pages 209~215
DOI : 10.4334/JKCI.2013.25.2.209
This study is aimed to identify the method to use the CaO-
system of rapidly cooled steel making slag (RCSS) as the environment-friendly inorganic accelerating agent by analyzing its physical and chemical properties. The fraction of rapidly cooled steel making slag is distinguished from its fibrous, and the contents of CaO and
are inversely proportional across different fractions. In addition, as the content of CaO decreased and the content of
increased, the loss ignition tended to become negative (-) and the density increased. The pore distribution by mercury intrusion porosimetry is very low as compared to the slowly cooled steel-making slag, which indicates that the internal defect and the microspore rate are remarkably lowered by the rapid cooling. To analyze the major minerals the rapidly cooled steel-making slag, XRD, f-CaO quantification and SEM-EDAX analysis have been performed. The results shows that f-CaO does not exist, and the components are mainly consisted of
Strengths of Lap Splices Anchored by SD600 Headed Bars
Chun, Sung-Chul ; Lee, Jin-Gon ;
Journal of the Korea Concrete Institute, volume 25, issue 2, 2013, Pages 217~224
DOI : 10.4334/JKCI.2013.25.2.217
Design provisions for the development length of headed bars in ACI 318-08 include concrete compressive strength and yield strength of headed bars as design parameters but do not consider the effects of transvers reinforcement. In addition, they have very strict limitation for clear spacing and material strengths because these provisions were developed based on limited tests. In this study, splice tests using SD600 headed bars with
clear spacing and transverse reinforcement were conducted. Test results show that unconfined specimens failed due to prying action and bottom cover concrete prematurely spalled. The contribution of head bearing on the anchorage strength is only 15% on average implying that unconfined specimens failed before the head bearing was not sufficiently developed. Confined specimens with stirrups placed along whole splice length have enhanced strengths in bearing as well as bond because the stirrups prevented prying action and improved bond capacity. Bond failure occurred in locally confined specimens where stirrups were placed only at the ends of splice length. The stirrups at ends of splice lengths can prevent prying action but the bond capacity did not increase. From regression analysis of test results, an equation to predict anchorage strength of headed bars was developed. The proposed equation consists of bond and bearing contributions and includes transverse reinforcement index. The average ratio of tests to predictions is 1.0 with coefficient of variation of 6%.
A Study on Strength Development Constant of Concrete for Performance Based Design
Choi, Yun-Wang ; Jeong, Jae-Gwon ; Park, Man-Seok ; Oh, Sung-Rok ; Lee, Kwang-Myong ;
Journal of the Korea Concrete Institute, volume 25, issue 2, 2013, Pages 225~232
DOI : 10.4334/JKCI.2013.25.2.225
The recent worldwide trend in construction industry tends to put emphasis on the performance based design which focuses on the suggestion of the performance of final products rather than method and procedures. A proper model should be employed when predicting the concrete strength, which reflects the material age, in order to verify the function of concrete structures and their materials. Accordingly, this paper proposes the concrete strength development constant (
) reflecting the characteristics of domestic materials and then evaluates its suitability.
A Study on Improvement of Seismic Performance of High Strength Reinforced Concrete Interior Beam-Column Joints Using High Ductile Fiber-Reinforced Mortar and Advanced Reinforcing Detailings
Ha, Gee-Joo ; Yi, Dong-Ryul ; Hong, Kun-Ho ;
Journal of the Korea Concrete Institute, volume 25, issue 2, 2013, Pages 233~240
DOI : 10.4334/JKCI.2013.25.2.233
In this study, experimental research was carried out to evaluate and improve the seismic performance of high strength R/C interior beam-column joints regions using advanced reinforcing detailings and high ductile fiber-reinforced mortar. Five specimens of retrofitted the beam-column joint regions using advanced reinforcing detailings and high ductile fiber-reinforced mortar were constructed and tested for their retrofitring performances. Specimens designed by retrofitting the interior beam-column joint regions (IJIR series) of existing reinforced concrete building showed a stable mode of failure and an increase in load-carrying capacity. Specimens of IJIR series, designed by the retrofitting of advanced reinforcing detailings and high ductile fiber-reinforced mortar in reinforecd beam-column joint regions increased its maximum load carrying capacity by 114.2~123.5% and its energy dissipation capacity by 1.55~1.85 times in comparison with the standard specimen of SIJC with a displacement ductility of 5.
Effect of Fly Ash on Rheology and Strength of Recycled Aggregate Concrete
Kim, Kyu-Hun ; Shin, Myoung-Su ; Kong, Young-Sik ; Cha, Soo-Won ;
Journal of the Korea Concrete Institute, volume 25, issue 2, 2013, Pages 241~250
DOI : 10.4334/JKCI.2013.25.2.241
As the amount of construction wastes increase, reuse of demolished concrete is being considered in research areas. Reflecting these interests, this experiment was performed to clarify concrete's mechanical property and workability using recycled aggregate as a coarse aggregate. Eleven cases of concrete specimens were produced by changing the rates of replacement of coarse recycled aggregate, replacement of fly ash, design strength, and moisture state of coarse aggregate. Compressive and tensile split strength tests were taken to study the mechanical properties of hardened concrete. To verify flowability of fresh concrete, a slump test and a flow curve test using ICAR Rheometer were performed. It was found that using recycled aggregate and fly ash leads good workability by testing slump and flow curve. The yield stress of fresh concrete decreased with increase of recycled aggregate substitution rate. Through the test, it was confirmed that there is inversely proportional relationship between the slump and yield stress roughly. Recycled aggregate concrete containing fly ash has considerably lower plasticity viscosity than not containing fly ash. Strength test results showed that recycled aggregate tended to decrease compressive and tensile strength of concrete, when recycled aggregate was used as a coarse aggregate. Using over 30% recycled aggregate caused significant decreases in compressive and tensile strength. Replacing 30% cement with fly ash was helpful to improve the long-term strength of concrete.