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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 13, Issue 6 - Dec 2001
Volume 13, Issue 5 - Oct 2001
Volume 13, Issue 4 - Aug 2001
Volume 13, Issue 3 - Jun 2001
Volume 13, Issue 2 - Apr 2001
Volume 13, Issue 1 - Feb 2001
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Fundamental Properties of Concrete Block and Brick using Casting foundry Fly Ash
Journal of the Korea Concrete Institute, volume 13, issue 2, 2001, Pages 87~92
DOI : 10.22636/JKCI.2001.13.2.87
Until now, disposal of casting foundry fly ash generally depends on reclamation. This is the great loss from a point of view saving of resources and utilizing industrial wastes. Therefore, a study on the use of fly ash as a substitute material for construction is necessary in order to utilize industrial wastes, to reduce cost of production, to improve quality in producing concrete products, and to protect environment from pollution. In this study, concrete products(hollow concrete block and concrete brick) using casting foundry fly ash as a substitute materials for cement, are produced. And experiments are conducted based on Korean Industrial Standards. Finally, the used methods of casting foundry fly ash as a substitute materials in industry are presented.
Bond Stress in Concrete Pilled Steel Tubular Column
Journal of the Korea Concrete Institute, volume 13, issue 2, 2001, Pages 93~98
DOI : 10.22636/JKCI.2001.13.2.93
CFT column has excellent structural properties due to the composite action between concrete and steel tube. The bond behavior between the constituent elements has to be found for analyzing the behavior of CFT column. A new model is necessary because most of existing models for bond stress-slip relationship of the deformed bar cannot be applied to the CFT column. Therefore, the objective of this research is to develop a new model related to the bond behavior of CFT column considering the relation between bond stress and vertical stress, and the distribution of lateral stress under the confinement created by steel casing. From equilibrium condition, the formula for relationship between bond stress and vertical stress is derived, and the relationship for the lateral stresses of the CFT column section is obtained by an Airy stress function. The experiments are performed for five CFT column specimens axially loading on concrete alone. The relation between bond strength and lateral stress is investigated from the regression analysis using the measured strains. Finally a new bond strength model is proposed, which is able to predict the relationship for the stress of each direction of CFT column loading on concrete.
Continuity for Double Tee Slabs
Journal of the Korea Concrete Institute, volume 13, issue 2, 2001, Pages 99~106
DOI : 10.22636/JKCI.2001.13.2.99
The main objective of this study is to develop a continuity of double tee slab with two modified dap-ends to solve the problems of excessive moment, slab depth, deflection, and joint cracking in the original simply supported double tee slab systems. The modified joint is produced in a combination with two slabs with modified dap and one rectangular beam. The modified joint can be justified as following different merits. The span capacity for a design load is increased, while the deflection of the slab is decreased due to the decrease of positive moment at the center span of the slab. The joint cracking between slab and beam, which occur frequently in the original slab systems of double tee will be reduced. No more additional form work is needed to cast topping concrete for continuity. Three point loading tests are performed on the specimens with a variable of an amount of main longitudinal reinforcement to evaluate flexural and shear behavior. Following conclusions are obtained from the experimental investigation. The continuity of double tee slab effectively is provided by placing longitudinal steel reinforcement in the topping concrete over the connection, and generally leads to an increase in span capacity of double tee slabs with reduced deflection. It is more effective to control the initial cracking at the connection than that of some simply supported double tee slab systems.
Crack Source location Technique for nam Concrete Beam using Acoustic Emission
Journal of the Korea Concrete Institute, volume 13, issue 2, 2001, Pages 107~113
DOI : 10.22636/JKCI.2001.13.2.107
This study was conducted preliminarily to develop the crack source location technique for plain concrete beam using acoustic emission(AE). Before the main experiment, the test of virtual An source location was achieved in plain concrete block. The sensor layout was mutually compared between triangular layout and rectangular layout. As the results of test, AE source location by triangular layout was evaluated more effective than that by rectangular layout. The specimen to apply he source location technique was man in total nine specimens (each three in 40 %, 50%, 60% of W/C ratio) which the experiment variable was the compressive strength level(W/C ratio). The bending loading method is selected by cyclic loadings to evaluate the degree of concrete damage. It is seen that Kaiser effect and Felicity effect exists through analysis of AE parameters in coming failure experiment. As a result of analyzing the felicity ratio(FR) values, it is shown that this values can be used for evaluating the degree of concerto damage. AE activity is started highly at the 70% of failure load without the compressive strength level. Thus considered by a index in constructing the system of the failure warning at application of the field structure. And the results compared the real cracking location with the source location has perceived by AE monitoring before it is appeared the primary crack by visual observation.
Manufacturing of Sintered Lightweight Aggregate using Paper Mill Sludge Ash
Journal of the Korea Concrete Institute, volume 13, issue 2, 2001, Pages 114~122
DOI : 10.22636/JKCI.2001.13.2.114
The purpose of this study was to manufacture sintered lightweight aggregate using paper sludge ash and to evaluate the qualities of the aggregate according to various mix proportions, conditions of pelletization and sintering. The paper sludge ash alone, due to its mineral and chemical compositions could not gain suitable expansion and strength. Hence, it was essential to add mineral additives such as clay, fly ash etc. The optimum muting ratio range determined in this study is as follows , paper sludge ash 30∼50 %, clay 30∼50 %, fay ash 0∼40 %, Paper sludge 0∼10% and hematite 2∼3 %(for manufacturing lightweight aggregate both for non-structural and structural concrete). It was possible to manufacture various lightweight aggregate whose dry specific gravity ranged about from 0.6 to 1.4 by using this optimum mixing ratio. From the test results of the qualities of aggregate, it showed that the 10% granules crushing value test and water absorption percentage ranged about 5∼10 ton and 10∼20%. Thus, it was favorably comparable to those of the imported aggregate. The manufactured lightweight aggregate could be used for structural concrete and non-structural concrete.
Experimental Study on the Properties of Concrete by the Kinds of Admixture and the Replacement Ratios of Activated Hwangtoh
Journal of the Korea Concrete Institute, volume 13, issue 2, 2001, Pages 123~129
DOI : 10.22636/JKCI.2001.13.2.123
Pozzolan is to improve the strength and the durability of concrete as a result of the pozzolanic reaction, Broadly speaking, pozzolanic materials can be artificial materials, such as slica fume and fly ash, and natural material, such as rice husk ash, clay, volcanic ash, clayish pozzolan. Hwangtoh is a mineral which belongs to a group of matakaolin, especially halloysite, and the main elements is SiO
. The purpose of this study is to examine the application of Hwangtoh for the concrete admixtures, the composition of this study is shown as follows. Chapter I is analysis for properties of concrete as the kinds of admixture, and Chapter H is analysis for properties of concrete as the replacement ratio of activated Hwangtoh. As a result of this study, Hwangtoh is found to have high practical use as pozzolanic material, and the pertinent range of replacement ratios of Hwangtoh on cement are 10∼20 %.
Shear Behavior Prediction of Reinforced Concrete Beams by Transformation Angle Truss Modul
Journal of the Korea Concrete Institute, volume 13, issue 2, 2001, Pages 130~138
DOI : 10.22636/JKCI.2001.13.2.130
This paper presents on the shear behavior prediction of reinforced concrete beams using Transformation Angle Truss Model (TATM). The TATM can evaluate the stress-strain relationships for cracked concrete by transforming stresses and strains for principal plane into those over the crack surfaces. This proposed analytical method simplifies the Fixed Angle Softened Truss Model (FA-STM) and removes the limitation of applicability of the FA-STM. The shear.strength and strain of reinforced concrete beams are predicted by using the TATM. For the verification of proposed method, experimental results of reinforced concrete beams were compared with theoretical results by the TATM, FA-STM and Rotating Angle Softened Truss Model (RA-STM).
Experimental Study on the Evaluation of frost-Resistance of High-Strength Concrete Damaged by frost at Early Age in Cold Climates
Journal of the Korea Concrete Institute, volume 13, issue 2, 2001, Pages 139~145
DOI : 10.22636/JKCI.2001.13.2.139
One of ways to make high-strength concrete is for the mix contain particles graded down to the finest size : this is achieved by the use of fly ash, silica fume which fills the spaces between the cement particle and between the aggregate and the cement particles. And, the mix needs a sufficient workability. This is achieved by the use of a superplasticizer. This study is to investigate frost resistance of high-strength concrete at early age, with ratio of tensile strength and recovery of compressive strength, when high-strength concrete is placed in cold climates. According to this study, it is necessary to ensure 4 % of air content, 5 kgf/
of tensile strength, at least, for frost resistance of high-strength concrete at early age.
Crack Growth Behavior of Cement Composites by Fractal Analysis
Journal of the Korea Concrete Institute, volume 13, issue 2, 2001, Pages 146~152
DOI : 10.22636/JKCI.2001.13.2.146
The fractal geometry is a non-Euclidean geometry which discribes the naturally irregular or fragmented shaps, so that it can be applied to fracture behavior of materials to investigate the fracture process. Fractal curves have a characteristic that represents a self-similarity as an invariant based on the fractal dimension. This fractal geometry was applied to the crack growth of cementitious composites in order to correlate the fracture behavior to microstructures of cemposite composites. The purpose of this study was to find relationships between fractal dimensions and fracture energy. Fracture test was carried out in order to investigate the fracture behavior of plain and fiber reinforced cement composites. The load-CMOD curve and fracture energy of the beams were observed under the three point loading system. The crack profiles were obtained by the image processing system. Box counting method was used to determine the fractal dimension, D
. It was known that the linear correlation exists between fractal dimension and fracture energy of the cement composites. The implications of the fractal nature for the crack growth behavior on the fracture energy, G
Size Effect on Axial Compressive Strength of Concrete
Journal of the Korea Concrete Institute, volume 13, issue 2, 2001, Pages 153~160
DOI : 10.22636/JKCI.2001.13.2.153
In this study, the size effect on axial compressive strength for concrete members was experimentally investigated. Experiment of mode I failure, which is one of the two representative compressive failure modes, was carried out by using double cantilever beam specimens. By varying the eccentricity of applied loads with respect to the axis on each cantilever and the initial crack length, the size effect of axial compressive strength of concrete was investigated, and new parameters for the modified size effect law (MSEL) were suggested using least square method (LSM). The test results show that size effect appears for axial compressive strength of cracked specimens. For the eccentricity of loads, the influence of tensile and compressive stress at the crack tip are significant and so that the size effect is present. In other words, if the influence of tensile stress at the crack tip grows up, the size effect of concrete increases. And the effect of initial crack length on axial compressive strength is present, however, the differences with crack length are not apparent because the size of fracture process zone (FPZ) of all specimens in the high-strength concrete is similar regardless of differences of specimen slenderness.
Fracture Properties of High Strength Concrete Disk with Center-Crack
Journal of the Korea Concrete Institute, volume 13, issue 2, 2001, Pages 161~167
DOI : 10.22636/JKCI.2001.13.2.161
It is difficult to obtain accurate fracture toughness values using three point bending test(TPB) proposed by RILEM committees because the shape of load-deflection curve is irregular and final crack propagation occurs after some slow stable cracking. However, fracture toughness is easily obtained from crack initiation load in the disk test. In this paper, the fracture properties of high strength concrete disks with center-crack was investigated. For this purpose, the experimental results were compared with the results by finite element analysis(FEA). And the experimental fracture locus was compared with theoretical fracture locus. Also, the results of fracture properties for the degree of concrete strength are presented. It is concluded from this study that results from FEA with maximum stress theory were compared well with the results from experiment. And the degree of concrete strength was contributed to the crack initiation load and fracture toughness, but was not contributed to the failure angle. Also, The discrepancy of fracture locus between the maximum stress theory and the experiment for concrete is considered to depend upon a large energy requirement for inducing the mixed-mode and sliding mode fractures.
Experimental Study on Bond Strength between Carbon Fiber Sheet and Concrete
Journal of the Korea Concrete Institute, volume 13, issue 2, 2001, Pages 168~174
DOI : 10.22636/JKCI.2001.13.2.168
Carbon fiber sheet(CFS) has been widely used for strengthening of the concrete building structures due to its excellent physical properties such as high strength, light weight and high durability. Bond strength or behavior, on the other hands, between carbon fiber sheet and concrete is very important in strengthening the concrete member using CFS. Therefore the bond failure mechanism between CFS and concrete should be fully verified and understood. This study is to investigate the bond strength of CFS to the concrete by the direct pull-out test and the tensile-shear test. In the direct pull-out tests, the bond strength under the various environmental conditions such as curing temperature, surface condition on concrete and water content of concrete are evaluated. Also, the effective bond length, lu and the average bond stress,
y are examined in the tensile-shear tests. Based on the test results, it is concluded that the curing temperature is the most critical element for the bond strength between CFS and concrete. And, the proper value of lu and
y is recommended with 15 cm and 9.78∼ 11.88 kgf/
Evaluation on the Deterioration and Resistance of Cement Matric due to Seawater Attack
Journal of the Korea Concrete Institute, volume 13, issue 2, 2001, Pages 175~183
DOI : 10.22636/JKCI.2001.13.2.175
Immersion tests with artificial seawater were carried out to investigate the resistance to seawater attack of 5 types of cement matrices. From the results of compressive strength and length change, it was found that blended cement mortars due to mineral admixtures, were superior to portland cement mortars with respect to the resistance to seawater attack. Moreover, XRD analysis indicated that the peak intensity ratio of low heat portland cement(LHC) paste, in portland cement pastes, had better results, and so did that of blended cement Paste. Pore volume of pastes by mercury intrusion porosimetry method demonstrated that total pore volume of ordinary portland cement(OPC) paste had a remarkable increase comparing with that of other pastes. In case of immersion of artificial seawater, the use of ground granulated blast-furnace slag and fly ash, however, showed the beneficial effects of 56% and 32% in reduction of total pore volume, respectively.
Experimental Study on Physical and Mechanical Properties of Concrete with fine Waste Glass
Journal of the Korea Concrete Institute, volume 13, issue 2, 2001, Pages 184~191
DOI : 10.22636/JKCI.2001.13.2.184
Recently, as industrialization is rapidly growing and the standard of life is rising, the quantities of waste glasses have been hastily increased and most of them are not recycled but abandoned. It cause some problems such as the waste of natural resources and environmental pollution. Therefore, this study was conducted basic experimental research to analyze the possibilities of recycling of waste glasses(crushed waste glasses outbreaking from our country such as amber, emerald-green, flint and mixed) as fine aggregates for concrete. Test results of fresh concrete, slump and compacting factors decrease because grain shape is angular and air content increase due to involving small size particles so much in waste glasses. Also compressive, tensile and flexural strengths decrease with increase of the content of waste glasses. In conclusion, the content of waste glasses below 30% is reasonable and usage of pertinent admixture is necessary to obtain workability and air content.