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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 19, Issue 6 - Dec 2007
Volume 19, Issue 5 - Oct 2007
Volume 19, Issue 4 - Aug 2007
Volume 19, Issue 3 - Jun 2007
Volume 19, Issue 2 - Apr 2007
Volume 19, Issue 1 - Feb 2007
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Demand Strength Spectrums of Low-Rise Reinforced Concrete Buildings Consisted of Extremely Brittle, Shear and Flexural Failure Systems
Lee, Kang-Seok ; Kim, Jeong-Hee ; Oh, Jae-Keun ;
Journal of the Korea Concrete Institute, volume 19, issue 5, 2007, Pages 529~537
DOI : 10.4334/JKCI.2007.19.5.529
The purpose of this study is to discuss how strength and ductility of each system in low-rise reinforced concrete buildings composed of extremely brittle, shear and flexural failure lateral-load resisting systems have influence on seismic capacities of the overall system, which is based on nonlinear seismic response analyses of single-degree-of-freedom structural systems. In order to simulate the triple lateral-load resisting system, structures are idealized as a parallel combination of two modified origin-oriented hysteretic models and a degrading trilinear hysteretic model that fail primarily in extremely brittle, shear and flexure, respectively. Stiffness properties of three models are varied in terms of story shear coefficients, and structures are subjected to various ground motion components. By analyzing these systems, interaction curves of demand strengths of the triple system for various levels of ductility factors are finally derived for practical purposes. The result indicates that demand strength levels derived can be used as a basic information for seismic evaluation and design criteria of low-rise reinforced concrete buildings having the triple lateral-load resisting system.
Properties of Polymer-Modified Pastes with Alumina Powder
Joo, Myung-Ki ; Lee, Youn-Su ; Yeon, Kyu-Seok ;
Journal of the Korea Concrete Institute, volume 19, issue 5, 2007, Pages 539~547
DOI : 10.4334/JKCI.2007.19.5.539
The effects of binder and alumina content on the setting time, drying shrinkage, strength, freezing and thawing resistance and water absorption of polymer-modified pastes with alumina powder were examined. As a result the setting time of the polymer-modified pastes with alumina powder tended to delay with increasing binder content. Irrespective of the type of polymer, the drying shrinkage of the polymer-modified pastes with alumina powder tended to decrease with increasing binder content and alumina powder content. Regardless of the type of polymer, the tensile and adhesion strengths of the polymer-modified pastes with alumina powder tended to increase with increasing binder content and alumina powder content. Irrespective of the type of polymer, the durability factors of the polymer-modified pastes with alumina powder tended to increase with increasing alumina content. Irrespective of the type of polymer, the water absorptions of the polymer-modified pastes with alumina powder tended to decrease with increasing binder content and alumina content.
The Properties of Underwater-Hardening Epoxy Mortar Used the Rapidly Cooled Steel Slag (RCSS)
Kim, Jin-Man ; Kwak, Eun-Gu ; Bae, Kee-Sun ;
Journal of the Korea Concrete Institute, volume 19, issue 5, 2007, Pages 549~555
DOI : 10.4334/JKCI.2007.19.5.549
Although blast furnace slag has been widely used in concrete as a cementitious admixture or aggregate for many years, the slowly cooled steel slag is not used in concrete but mainly in road. Its use in concrete operates problem such as the lack of volume stability due to high free CaO content, which can be potentially hazardous in concrete. However, the rapidly cooled steel slag by atomization has a low free CaO content, a high density, and a spherical shape, so it is expected to use in concrete so much. This paper is to understand the probability that the rapid cooled steel slag can replace the silica sand used as aggregate in the epoxy mortar. We did the experimental study on the properties of the epoxy mortar having various replacement proportion of rapidly cooled steel slag. This study shown that increasing content of the rapidly cooled steel slag in epoxy mortar lead to increase largely the passing time of nozzle by O-lot, compressive strength and flexural strength. However except the flow is almost same level. So we understand that the rapidly cooled steel slag has positive effect on increasing of properties in epoxy mortar.
Flexural Behavior of Hybrid Beam of Reduced Story Height
Hong, Sung-Gul ; Yang, Dong-Hyun ; Jung, Jong-Hyun ; Yim, Byung-Ho ;
Journal of the Korea Concrete Institute, volume 19, issue 5, 2007, Pages 557~567
DOI : 10.4334/JKCI.2007.19.5.557
In underground parking lots of apartment housing, the story height is increased by
because of various ducts for HVAC. In order to reduce this story height, this study proposed the 'hybrid beam', which is composed of PC beam with embedded steel beam and insitu concrete. The depth of the hybrid beam is reduced by 300 mm and then the steel beam is embedded over the length of reduced depth to compensate for the loss of strength. Then, we performed the large-scale structural tests on 9 specimens and investigated the flexural behavior of the specimens. The parameters of tests were the shape of steel beam section, the length of the reduced depth, the stage of construction, the effects of slab and shear connectors. The test results showed that the specimens, after the insitu concrete has cured, has the flexural capacity which exceeds the required design capacity regardless of other parameters. On the other hand, the specimens of construction stage do not have sufficient strength. Based on these results, it is thought that the proposed hybrid beam with reduced depth is applicable to the underground parking lots of apartment housing as long as the support is placed at construction stage.
An Experimental Study on the Flexural Behavior of One-Way Concrete Slabs Using the Restorative Mortar and Crimped Wire Mesh
Lee, Mun-Hwan ; Song, Tae-Hyeob ;
Journal of the Korea Concrete Institute, volume 19, issue 5, 2007, Pages 569~575
DOI : 10.4334/JKCI.2007.19.5.569
The repair of concrete surfaces does not normally take into account structural tolerance for longer service lift and better capabilities of concrete structures. In particular, the repair of surface spelling completes as mortar is applied, which does not display additional structural performances. The use of crimped wire mesh for better construction and fracture resistance, however, expects to have some reinforcement effects. Particularly, it is also expected that the repair of bottom part in structures built between bridges like irrigation structures results in the increase of flexural resistance. Therefore, this study is intended to perform the repair using crimp wire mesh and examine strength depending on the repair section and depth. For this, a slab with 150 mm in depth, 3,000 mm in length and 600 mm in width and total 8 objects to experiment such as upper part, upper whole, bottom part, bottom whole and crimp wire mesh reinforced are manufactured to perform flexural performance. The results of the analysis show that yield strength and failure load increase as the depth of repair materials in the experiment reinforced with crimp wire mesh get bigger. In the same condition, repair of bottom part is able to increase internal force of bending force. Besides, the results show that partial repair of structures under bending force cannot produce flexural performance. Consequently, the repair method with crimp wire mesh results in the increase of flexural resistance.
Effect of Mechanical Restraint due to Steel Microfibers on Alkali-Silica Reaction in Mortars
Yi, Chong-Ku ;
Journal of the Korea Concrete Institute, volume 19, issue 5, 2007, Pages 577~584
DOI : 10.4334/JKCI.2007.19.5.577
The effect of steel microfibers (SMF) on alkali-silica reaction (ASR) was investigated using two types of reactive aggregates, crushed opal and a pyrex rod of constant diameter. Cracks are less visible in the SMF mortars compared with the unreinforced mortars. Due to crack growth resistance behavior in SMF mortar specimens, the strength loss is eliminated and the ASR products remained well confined within the ASR site. The expansion and the ASR products were characterized by microprobe analysis and inductively coupled plasma (ICP) spectroscopy. The confinement due to SMF resulted in a higher Na and Si ion concentration of the ASR liquid extracted from the reaction site. The higher concentration reduced the ASR rate and resulted in a lower reactivity of the reactive pyrex rods in SMF mortars.
Time Dependent Chloride Transport Evaluation of Concrete Structures Exposed to Marine Environment
Song, Ha-Won ; Pack, Seung-Woo ; Ann, Ki-Yong ;
Journal of the Korea Concrete Institute, volume 19, issue 5, 2007, Pages 585~593
DOI : 10.4334/JKCI.2007.19.5.585
This paper presents a model for durability evaluation of concrete structures exposed to marine environment, considering mainly a build-up of surface chloride
as well as diffusion coefficient (D) and chloride threshold level
. In this study, time dependency of
and D were extensively studied for more accurate evaluation of service life of concrete structures. An analytical solution to the Fick's second law was presented for prediction of chloride ingress for time varying
. For the time varying
, a refined model using a logarithm function for time dependent
was proposed by the regression analysis, and averaging integrated values of the D with time over exposed duration were calculated and then used for prediction of the chloride ingress to consider time dependency of D. Durability design was also carried out for railway concrete structures exposed to marine environment to ensure 100 years of service life by using the proposed models along with the standard specification on durability in Korea. The proposed model was verified by the so-called performance-based durability design, which is widely used in Europe. Results show that the standard specification underestimates durability performances of concrete structures exposed to marine environment, so the cover depth design using current durability evaluation in the standard specifications is very much conservative. Therefore, it is found that utilizing proposed models considering time dependent characteristics of
and D can evaluate service lift of concrete structures in marine environment more accurately.
A Study on Strengthening of Reinforced Concrete Pier Caps Using Prestressed Near Surface Mounted CFRP
Hong, Sung-Nam ; Kim, Tae-Wan ; Park, Sun-Kyu ; Park, Jong-Sup ; Park, Young-Hwan ;
Journal of the Korea Concrete Institute, volume 19, issue 5, 2007, Pages 595~602
DOI : 10.4334/JKCI.2007.19.5.595
Recently, concrete structures with carbon fiber reinforced polymer (CFRP) reinforcements have been commonly used for the bridge and building construction. In this paper, pier caps were strengthened by prestressed near surface mounted CFRP. To verify the effectiveness of the strengthening method, 7 pier cap specimens were fabricated. One specimen was designed for control, two for external prestressing steel strands, two for CFRP plates, and two for CFRP bars. Experimental variables consist of type of reinforcement materials and prestressing levels. The results of laboratory have shown that the ultimate load capacities of prestressed near surface mounted CFRP specimens were about
greater than that of a control specimen. Also, ultimate load capacities of prestressed near surface mounted CFRP specimens were similar to those of external prestressing specimens with steel strands.
Tests for Moment Redistribution in Flat Plates with Different Reinforcement Details according to End and Midspan Moment Distributions
Choi, Jung-Wook ; Song, Jin-Kyu ;
Journal of the Korea Concrete Institute, volume 19, issue 5, 2007, Pages 603~611
DOI : 10.4334/JKCI.2007.19.5.603
Three interior slab-column connections designed by equal static moments and by different distribution of end and midspan moments were tested. Each test specimen consists of a 4.2 m square slab and a 355 mm square column stub. The slab thickness is 152 mm. Test results showed not only that flat plate systems can undergo considerable redistribution of moments from the uncracked state to final maximum capacity, but also that the distribution of moments is controlled largely by the distribution of reinforcement adopted by the designer. Tests also indicated that the punching shear strength of slabs can be affected by the redistributed moments.
A Study on Change in Cement Mortar Characteristics under Carbonation Based on Tests for Hydration and Porosity
Kwon, Seung-Jun ; Song, Ha-Won ; Park, Sang-Soon ;
Journal of the Korea Concrete Institute, volume 19, issue 5, 2007, Pages 613~621
DOI : 10.4334/JKCI.2007.19.5.613
Due to the increasing significance of durability, much researches on carbonation, one of the major deterioration phenomena are carried out. However, conventional researches based on fully hardened concrete are focused on prediction of carbonation depth and they sometimes cause errors. In contrast with steel members, behaviors in early-aged concrete such as porosity and hydrates (calcium hydroxide) are very important and may be changed under carbonation process. Because transportation of deteriorating factors is mainly dependent on porosity and saturation, it is desirable to consider these changes in behaviors in early-aged concrete under carbonation for reasonable analysis of durability in long term exposure or combined deterioration. As for porosity, unless the decrease in
diffusion due to change in porosity is considered, the results from the prediction is overestimated. The carbonation depth and characteristics of pore water are mainly determined by amount of calcium hydroxide, and bound chloride content in carbonated concrete is also affected. So Analysis based on test for hydration and porosity is recently carried out for evaluation of carbonation characteristics. In this study, changes in porosity and hydrate
under carbonation process are performed through the tests. Mercury Intrusion Porosimetry (MIP) for changed porosity, Thermogravimetric Analysis (TGA) for amount of
are carried out respectively and analysis technique for porosity and hydrates under carbonation is developed utilizing modeling for behavior in early-aged concrete such as multi component hydration heat model (MCHHM) and micro pore structure formation model (MPSFM). The results from developed technique is in reasonable agreement with experimental data, respectively and they are evaluated to be used for analysis of chloride behavior in carbonated concrete.
Development of Green Cement Type Grouting Materials with High Toughness and Non-Shrinkage Including Powder of Waste Tire and Resin
Park, Seok-Kyun ;
Journal of the Korea Concrete Institute, volume 19, issue 5, 2007, Pages 623~630
DOI : 10.4334/JKCI.2007.19.5.623
Grouting materials are used for the unification of superstructural and substructural body like bridge seat (shoe) or machinery pedestal and e.t.c by filling their intercalary voids. Accordingly, grouting materials have been developed and used mainly with products of high strength because those materials are constructed specially in a part receiving large or impact load. In this situation, the structural body constructed by grouting materials with high stiffness-centered (caused by high strength) products is apt to cause brittle failure when receiving over a limit stress and to cause cracks according to cumulative fatigue by continuous and cyclic load. In addition, grouting materials are apt to cause cracks by using too much rapid hardening agents that give rise to high heat of hydration to maintain high strength at early age. In this study, to overcome these problems, cement type grouting materials including powder of waste tire and resin as elastic materials which aim to be more stable construction and to be improvement of mother-body's unification are developed and endowed with properties of high toughness and high durability add to existing properties of high flowability, non-shrinkage and high strength. Besides, this study contribute to of for green construction materials for being possible recycling industrial waste like waste tire and flyash. On the whole, seven type mixing conditions are tested and investigated to choose the best mixing condition.
Bond Properties of High Strength Steel Rebar in High Strength Steel Fiber Reinforced Concrete
Won, Jong-Pil ; Park, Chan-Gi ; Jang, Chang-Il ; Lee, Sang-Woo ; Kim, Wan-Young ;
Journal of the Korea Concrete Institute, volume 19, issue 5, 2007, Pages 631~637
DOI : 10.4334/JKCI.2007.19.5.631
This study was to evaluate bond properties between high-strength steel fiber reinforced concrete and high strength steel rebar. An direct bond test were performed to evaluate the bond performance of high strength steel rebar in two types of high-strength concrete with steel fiber volume fraction (0, 20,
). Also, relative bond strength was defined to determine the effect of steel fiber volume fraction on bond strength. The bond test results showed that the bond performance of high strength steel rebar and high strength concrete tended to increase with higher compressive strength and steel fiber volume fraction. Relative bond strength which performed to analyze effect of steel fiber volume fraction showed increased relative bond strength with increased steel fiber volume fraction.
Durability Characteristics of Concrete with Nano Level Ceramic Based Coating
Kim, Seong-Soo ; Lee, Jeong-Bae ; Han, Seung-Woo ;
Journal of the Korea Concrete Institute, volume 19, issue 5, 2007, Pages 639~646
DOI : 10.4334/JKCI.2007.19.5.639
This study performed several tests for the durability of the concrete coated with nano synthesis ceramics which do not contain volatile organic compounds harmful to environment. The tests were adhesion test on dry and humid concrete, SEM test, MIP analysis, carbonation, chloride diffusion by electronic facilitation, freezing-thawing resistance, alkaline resistance, and brine resistance test. In the adhesion test on dry and humid concrete, nano synthesis ceramics coating produced the highest results among all the coatings tested. Nano synthesis ceramics adhered solidly on the concrete surface. The adhesive strength seemed to result from the hydrogen bond between nano synthesis ceramics which are inorganic and generated by hydrolysis and re-condensation reaction and the concrete's hydrates such as calcium silicate aluminate or calcium silicate hydrate. SEM test and MIP analysis results show surface structure with finest crevices pore in the nano synthesis ceramics coating applied concretes. In the carbonation, chloride diffusion, and freezing-thawing resistance tests, the concretes with nano synthesis ceramics coating indicated the best results. Based on these test results, further progress in application of nano synthesis ceramics coatings to various concrete structures including costal structures and sewerage arrangements can be expected.
Experimental Study of Freezing Characteristics and Antifreezing Method of Liquid Additive for Early Strength
Lee, Mun-Hwan ; Ryu, Deug-Hyun ;
Journal of the Korea Concrete Institute, volume 19, issue 5, 2007, Pages 647~653
DOI : 10.4334/JKCI.2007.19.5.647
In ready mixed concrete factory, in case of using the high molecular additive in winter especially the liquid additive for the early strength, it is required to check the stability. In this research, the freezing and gelling characteristics of the liquid additive for the early strength is reviewed, the material and mechanical solution are proposed to that the practical quality control method will be suggested. As the result, the Freezing temperature of the liquid additive for the early strength is
, and it is the lower than the temperature at which the strength is shown. By making with sodium silicate of
in 0.31 of mol ratio, it minimizes the gelling at the lower temperature. On the other hand, facilities for storing and supplying the material should be set at
so the temperature distribution is well spreaded for practical operation.
Plasticity Model for Directionality of Concrete Crack Damages
Kim, Jae-Yo ; Park, Hong-Gun ;
Journal of the Korea Concrete Institute, volume 19, issue 5, 2007, Pages 655~664
DOI : 10.4334/JKCI.2007.19.5.655
The inherent characteristic of concrete tensile cracks, directional nonlocal crack damage, causes so-called rotating tensile crack damage and softening of compressive strength. In the present study, a plasticity model was developed to describe the behavior of reinforced concrete planar members In tension-compression. To describe the effect of directional nonlocal crack damage, the concept of microplane model was combined with the plasticity model. Unlike existing models, in the proposed model, softening of compressive strength as well as the tensile crack damage were defined by the directional nonlocal crack damage. Once a tensile cracking occurs, the microplanes of concrete are affected by the nonlocal crack damage. In the microplanes, microscopic tension and compression failure surfaces are calculated. By integrating the microscopic failure surfaces, the macroscopic failure surface is calculated. The proposed model was implemented to finite element analysis, and it was verified by comparisons with the results of existing shear panel tests.