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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 24, Issue 6 - Dec 2012
Volume 24, Issue 5 - Oct 2012
Volume 24, Issue 4 - Aug 2012
Volume 24, Issue 3 - Jun 2012
Volume 24, Issue 2 - Apr 2012
Volume 24, Issue 1 - Feb 2012
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An Experimental Study on Pumpability Characteristics of High Strength Concrete Mixed Polymix
Lee, Joo-Ho ; Moon, Hyung-Jae ; Kim, Jeong-Jin ;
Journal of the Korea Concrete Institute, volume 24, issue 5, 2012, Pages 509~516
DOI : 10.4334/JKCI.2012.24.5.509
The aims of this research is to develop a fire resistant admixture to enhance high-pressured pumping of high-strength concrete (HSC) with a compressive strength of 60~80 MPa. Generally, the efficiency of HSC high-pressured pumping is dramatically reduced due to entanglement of short fibers added to prevent fire spalling. Therefore, the fire resistant admixture that can facilitate pumping of fire resistant HSC is urgently needed presently. The fire resistant HSC mix is comprised of Polypropylene fiber, Nylon fiber and Polymer powder. The test results showed that the slump-flow was improved by approximately 70% of the HSC without fire resistant admixture. However, the air void content was increased slightly due to the addition. The standard design compressive strength at 28-days was satisfied, while its flexural strength was similar to the concrete without the admixture. Since the flexural strength was 12~15% of its compressive strength, the general trend of flexural to compressive strength ratio in normal concrete was maintained. Even though its elastic modulus was decreased by adding the admixture, the study results showed that the concrete can be used for construction since all of the test results exceeded the code requirements.
Pushover Analysis of a 5-Story RC OMRF Considering Inelastic Shear Behavior of Beam-Column Joint
Kang, Suk-Bong ; Kim, Tae-Yong ;
Journal of the Korea Concrete Institute, volume 24, issue 5, 2012, Pages 517~524
DOI : 10.4334/JKCI.2012.24.5.517
In this study, the effects of the inelastic shear behavior of beam-column joint and the vertical distribution of lateral load are evaluated considering higher modes on the response of RC OMRF using the pushover analysis. A structure used for the analysis was a 5-story structure located at site class SB and seismic design category C, which was designed in accordance with KBC2009. Bending moment-curvature relationship for beam and column was identified using fiber model. Also, bending moment-rotation relationship for beam-column joint was calculated using simple and unified joint shear behavior model and moment equilibrium relationship for the joint. The results of pushover analysis showed that, although the rigid beam-column joint overestimated the stiffness and strength of the structure, the inelastic shear behavior of beam-column joint could be neglected in the process of structural design since the average response modification factor satisfied the criteria of KBC2009 for RC OMRF independent to inelastic behavior of joint.
Comparison of Flexural Tensile Strength according to the Presence of Notch and Fiber Content in Ultra High Performance Cementitious Composites
Kang, Su-Tae ;
Journal of the Korea Concrete Institute, volume 24, issue 5, 2012, Pages 525~533
DOI : 10.4334/JKCI.2012.24.5.525
In this study, bending tests were performed on beam specimens made of UHPCC with the fiber content range of 0~5 vol% to investigate the contribution of fiber content to first cracking strength and flexural tensile strength. Also, four-point bending tests for unnotched beam as well as three-point bending test for notched beam were performed to estimate the effect of the presence of notch on the strengths. The experiment result showed that the increase in fiber content made linear improvement in the flexural tensile strength; whereas first cracking strength was enhanced only when at least 1 vol% of fibers was incorporated. Comparison of the bending test results with and without notch showed that the notch effect varied with the fiber content. The increase in fiber content diminished the effect of stress concentration on the notch tip, reducing the difference in the strengths. With much higher fiber content, the effect of stress concentration almost disappeared and the defection on cracking plane or the size effect dominated the strengths, consequently resulting in higher strengths in the notched beams than the unnotched ones.
Equipment for Measuring the Adiabatic Temperature Rise of Concrete by Compensating Heat Loss
Jin, Eun-Woong ; Kim, Chin-Yong ; Kim, Jin-Keun ;
Journal of the Korea Concrete Institute, volume 24, issue 5, 2012, Pages 535~542
DOI : 10.4334/JKCI.2012.24.5.535
Adiabatic temperature rise test for predicting heat of hydration in mass concrete is especially inconvenient in the field. In order to overcome the problem, the equipment to effectively and conveniently measure semi-adiabatic temperature change was developed. The main objective of this paper is to propose a new and simple equipment for measuring semi-adiabatic temperature rise by using insulation bottles. In order to predict exact heat loss of concrete using this device, it is required to assume the specific heat loss coefficient of the device by water temperature change inside the experimental device. According to experimental and analytical results, the adiabatic temperature rise does not have significant differences in changes of temperature and humidity of air, as well as initial temperature of water. By comparing adiabatic temperature rise tests, the equipment for measuring semi-adiabatic temperature change can be used to predict the hydration heat of concrete within sufficient accuracy.
Strength Development of Fiber Reinforced Lean Concrete Using Fly Ash and Reject Ash under Different Compaction Methods including Small Scale Roller Vibrator
Kim, Seung-Won ; Jang, Young-Jae ; Park, Young-Hwan ; Park, Cheol-Woo ;
Journal of the Korea Concrete Institute, volume 24, issue 5, 2012, Pages 543~551
DOI : 10.4334/JKCI.2012.24.5.543
Road pavements in Korea generally show shorter service life than the predicted one. There are many reasons for this phenomenon including increased traffic load and other attacks from exposure conditions. In order to extend a service life and upgrade the pavement, a new multi-functional composite pavement system is being developed in Korea. This study is to investigate the performances of fiber-reinforced lean concrete for pavement base. This study considered mineral admixtures of fly ash and reject ash. The reject ash is defined as ash that does not meet the specifications for fly ash so that it cannot be used as a supplemental material for cement replacement. Due to the inherent property of lean concrete, compaction during the fabrication of specimens is a key factor. Therefore, this study suggests an appropriate compaction method. From the test results, the compressive strengths of the concrete satisfied the required limit of 5 MPa at 7 days. When a compaction roller was used to mimic actual field conditions, the strength development seemed to be influenced by the compaction energy rather than hydration of cement itself.
Penetration Properties of Airborne Chlorides on Concrete Exposed in Marine Environment
Lee, Jong-Suk ; An, Gi-Hong ;
Journal of the Korea Concrete Institute, volume 24, issue 5, 2012, Pages 553~558
DOI : 10.4334/JKCI.2012.24.5.553
Airborne chlorides are transported to inland by sea wind to be attached to seashore concrete structure surface then penetrated into concrete structure members. Since the surface attached chloride amount are dependent on the amount of airborne chlorides, the prediction of distribution of airborne chlorides is important information in preventing chloride corrosion problems in seashore concrete structures. The prediction of surface chloride amount from airborne chlorides environment is extremely difficult than concrete directly in contact with seawater. In addition, their penetrating tendency is different from that of concrete immersed in seawater. In this study, properties of surface and penetrated chlorides under airborne chlorides environment are investigated. Concrete specimens were manufactured and exposed to marine environment for 3 years. The specimens were analyzed at the time durations of 1, 2, and 3 years to check surface chloride amount to penetrated chloride depth. The results revealed that there were certain differences according to surface roughness of concrete and with and without washing effect due to rainfalls. The evaluation results showed that penetrated chlorides depend on amount of airborne chlorides and duration of exposure. In addition, a notable tendency of having deeper chloride penetration and higher chloride content in concrete members under long-term exposure was observed.
Nonlinear Modeling of RC Shear Walls Using Fiber and Shear Spring Elements
Lee, Kwang-Ho ; You, Tae-Sang ; Kim, Tae-Wan ; Jeong, Seong-Hoon ;
Journal of the Korea Concrete Institute, volume 24, issue 5, 2012, Pages 559~566
DOI : 10.4334/JKCI.2012.24.5.559
In this study, fiber elements and a spring are used to build a reinforced concrete shear wall model. The fiber elements and the spring reflect flexural and shear behaviors of the shear wall, respectively. The fiber elements are built by inputting section data and material properties. The spring parameters representing strength and stiffness degradation, pinching, and slip were determined by comparing behaviors of fiber element and VecTor2 results. `Pinching4` model in OpenSees is used for shear spring. The parameter selecting process for shear spring is a complicated and time consuming process. To study the applicability of the fiber element, reinforced concrete buildings containing a shear wall are evaluated using nonlinear dynamic analysis with various wall aspect ratio (H/L), various beam heights, and stiffness and flexural strength of beam and wall ratios. The aspect ratio of the wall showed distinct difference in IDR (interstory drift ratio) of the models with and without spring. On the other hand, the height of beam and ratio of stiffness and flexural strength of beam and wall did not show clear relation.
Heat Transfer Analysis and Experiments of Reinforced Concrete Slabs Using Galerkin Finite Element Method
Han, Byung-Chan ; Kim, Yun-Yong ; Kwon, Young-Jin ; Cho, Chang-Geun ;
Journal of the Korea Concrete Institute, volume 24, issue 5, 2012, Pages 567~575
DOI : 10.4334/JKCI.2012.24.5.567
A research was conducted to develop a 2-D nonlinear Galerkin finite element analysis of reinforced concrete structures subjected to high temperature with experiments. Algorithms for calculating the closed-form element stiffness for a triangular element with a fully populated material conductance are developed. The validity of the numerical model used in the program is established by comparing the prediction from the computer program with results from full-scale fire resistance tests. Details of fire resistance experiments carried out on reinforced concrete slabs, together with results, are presented. The results obtained from experimental test indicated in that the proposed numerical model and the implemented codes are accurate and reliable. The changes in thermal parameters are discussed from the point of view of changes of structure and chemical composition due to the high temperature exposure. The proposed numerical model takes into account time-varying thermal loads, convection and radiation affected heat fluctuation, and temperature-dependent material properties. Although, this study considered standard fire scenario for reinforced concrete slabs, other time versus temperature relationship can be easily incorporated.
Effects of Basicity on the Carbonation Characteristics of Alkali-Activated Slag Mortar
Song, Keum-Il ; Lee, Bang-Yeon ; Hong, Geon-Ho ; Gong, Min-Ho ; Song, Jin-Kyu ;
Journal of the Korea Concrete Institute, volume 24, issue 5, 2012, Pages 577~584
DOI : 10.4334/JKCI.2012.24.5.577
Carbonation resistance is one of the most influencing factors on durability of concrete. Alkali activated slag (AAS) is known to have weaker resistance for carbonation than OPC due to the low calcium contents. In this paper, the carbonation characteristic of AAS mortar which is related to the basicity (CaO/
) was investigated. In order to give the various basicity conditions, SM (source material) was blended with quicklime (CaO) and silicon dioxide (
) by adopting mechano-chemical treatment method. Experiments including flow test, compressive strength test, carbonation depth test, together with XRD, FTIR and TGA were employed to evaluate the effects of basicity of SM on the carbonation characteristics. The test results showed that the carbonation resistance effectively increased with the increase of the basicity of SM.
Flexural Characteristics of Reinforced Polymer Concrete T-Beams Strengthened with GFRP
Jin, Nan-Ji ; Hwang, Hae-Geun ; Yeon, Jung-Heum ;
Journal of the Korea Concrete Institute, volume 24, issue 5, 2012, Pages 585~596
DOI : 10.4334/JKCI.2012.24.5.585
In this study, the flexural characteristics of reinforced polymer concrete T-beams strengthened with GFRP, typically used for bridges and parking structures, are investigated. A method to determine the flexural failure mode of reinforced polymer concrete T-beams comprised of compression failure (CF), tension failure (TF), and fiber sheet failure (FF) for different levels of GFRP strengthening is proposed. Moreover, the present study provides a formula to calculate the design flexural strength for each failure mode. In reinforced polymer concrete T-beams strengthened with GFRP, an ideal failure mode can be achieved when the failure occurs in the following order: 1) yield of steel reinforcement, 2) failure of GFRP, and 3) compression failure of concrete. In the case of FF mode, due to GFRP failure before the polymer concrete crushing in compression region, a concept of equivalent rectangular block based on the ultimate limit state of concrete should not be used. Thus, this study suggests an idealized stress-strain curve for polymer concrete and finds parameters for stress block,
based on the strain distribution in polymer concrete. Furthermore, the present study suggests an aspect ratio of 2.5 by examining the compressive stress distribution and design flexural strength characteristics for different aspect ratio of T-beams. This study also provides a design flexural strength formula, and validates its acceptability based on experiment and theoretical analysis.
Design of Supplementary Cementitious Materials and Unit Content of Binder for Reducing CO
Emission of Concrete
Yang, Keun-Hyeok ; Moon, Jae-Heum ;
Journal of the Korea Concrete Institute, volume 24, issue 5, 2012, Pages 597~604
DOI : 10.4334/JKCI.2012.24.5.597
The present study assessed the
emissions of concrete according to the type and replacement ratio of supplementary cementitious materials (SCM) and concrete compressive strength using a comprehensive database including 2464 cement concrete specimens and 776 cement concrete mixes with different SCMs. The system studied in
assessment of concrete based on Korean lifecycle inventory was from cradle to pre-construction, which includes consistent materials, transportation and production phases. As the performance efficiency indicators, binder and
intensities were analyzed, and simple equations to evaluate the amount of
emission of concrete were then formulated as a function of concrete compressive strength and the replacement ratio of each SCM. Hence, the proposed equations are expected to be practical and useful as a guideline to determine the type and replacement ratio of SCM and unit content of binder in concrete mix design that can satisfy the target compressive strength and
reduction percentage relative to cement concrete.
Evaluation of Spalling Property and Water Vapor Pressure of Concrete with Heating Rate
Choe, Gyeong-Cheol ; Lee, Tae-Gyu ; Nam, Jeong-Soo ; Park, Byung-Keun ; Kim, Gyu-Yong ;
Journal of the Korea Concrete Institute, volume 24, issue 5, 2012, Pages 605~612
DOI : 10.4334/JKCI.2012.24.5.605
Spalling of concrete occurs due to vapor pressure ignited explosion, temperature difference across a section, and combination of these factors. Factors affecting spalling can be classified into internal and external factors such as material property and environmental condition, respectively, have to be considered to precisely understand spalling behavior. An external environmental factor such as differences in heating rate cause internal humidity cohesion and different vapor pressure behavior. Therefore, spalling property, vapor pressure and thermal strain property were measured from concrete with compressive strengths of 30 MPa, 50 MPa, 70 MPa, 90 MPa, and 110 MPa, applied with ISO-834 standard heating curve of
heating rate. The experimental results showed that spalling occurred when rapid heating condition was applied. Also, when concrete strength was higher, the more cross section loss from spalling occurred. Also, spalling property is influenced by first pressure cancellation effect of thermal expansion caused by vapor pressure and heating rates.
Study on Corrosion and Structural Performance in Hot-Dip Galvanizing Steel
Kwon, Seung-Jun ; Lee, Sang-Min ; Lee, Myung-Hoon ; Park, Sang-Soon ;
Journal of the Korea Concrete Institute, volume 24, issue 5, 2012, Pages 613~621
DOI : 10.4334/JKCI.2012.24.5.613
Steel corrosion is one of the most critical deteriorations in concrete structures due to the problems associated with both durability and structural safety issues. For protection of steel against corrosion problems, researches to improve concrete durability and steel corrosion protection such as rebar coating by hot-dip galvanizing steel have been carried out. This study was performed to quantitatively evaluate anti-corrosion and structural performance of concrete structures reinforced with hot-dip galvanizing steel rebar. Preliminary tests for several metal coatings such as zinc, aluminum, and their alloy (Zn 45% + AL 55%) were performed. After evaluation of corrosive characteristics, Zn was selected for the coating material and the corrosion behaviors in Zn-coated steel were evaluated in various conditions. Furthermore, tensile and adhesive strengths were evaluated for the normal and the hot-dip galvanized steel. The crack patterns and structural behaviors of RC specimens with the normal and coated steel were investigated. Also, corrosion characteristics including corrosion in various coating metal and potential change in metal with notch were evaluated. Structural performances of tensile and adhesive strengths as well as RC beam behavior under flexural/shear loading were evaluated. The test and evaluation results showed that the applicability of hot-dip galvanized steel rebar can be used as corrosion resistant reinforcements for RC structures.