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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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International Journal of Concrete Structures and Materials
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Korea Concrete Institute
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Volume & Issues
Volume 5, Issue 2 - Dec 2011
Volume 5, Issue 1 - Jun 2011
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An Experimental Study of Reinforced Concrete Beams with Closely-Spaced Headed Bars
Lam, Kah Mun ; Kim, Woo-Suk ; Van Zandt, Michael ; Kang, Thomas H.K. ;
International Journal of Concrete Structures and Materials, volume 5, issue 2, 2011, Pages 77~85
DOI : 10.4334/IJCSM.2011.5.2.77
The use of headed bars as opposed to standard 90- or 180-degree hooked bars in beam ends, beam-column joints or other steel congested areas for anchorage and bond has become more favorable due to the fact that steel congestion is often created by large bend diameters or crossties. This research mainly focuses on evaluating the code provisions regarding the use of headed bars. Nine simply supported rectangular concrete beams with headed longitudinal reinforcement were tested under a four-point monotonic loading system. The design clear spacing, which varies from 1.5 to 4.25 times the bar diameter, was the only parameter for the experimental investigation. The test results showed that the closely-spaced headed bars were capable of developing to full yield strength without any severe brittle concrete breakout cone or pullout failure. Bond along the bar was not sufficient due to the early loss of concrete integrity. However, the headed bars were effective for anchorage with no excessive moment capacity reduction. This implies that the clear spacing of about 2 times the bar diameter for headed bars may be reasonable to ensure the development of specified yield strength of headed bars and corresponding member design strength.
Revision on Material Strength of Steel Fiber-Reinforced Concrete
Karl, Kyoung-Wan ; Lee, Deuck-Hang ; Hwang, Jin-Ha ; Kim, Kang-Su ; Choi, Il-Sup ;
International Journal of Concrete Structures and Materials, volume 5, issue 2, 2011, Pages 87~96
DOI : 10.4334/IJCSM.2011.5.2.87
Many studies have been performed on steel fiber-reinforced normal/high-strength concrete (SFRC, SFRHC) for years, which is to improve some of the weak material properties of concrete. Most of equations for material strengths of SFRHC, however, were proposed based on relatively limited test results. In this research, therefore, the material test results of SFR(H)C were extensively collected from literature, and material tests have conducted on SFR(H)C; compressive strength tests, splitting tensile tests, and modulus of rupture tests. Based on the extensive test data obtained from previous studies and this research, a database of SFR(H)C material strengths has been established, and improved equations for material strengths of SFR(H)C were also proposed. Test results showed that both the splitting tensile strength and the modulus of rupture of SFR(H)C increased as the volume fraction of steel fiber increased, while the effect of the steel fiber volume fraction on the compressive strength of SFR(H)C were not clearly observed. The proposed equations for the splitting tensile strength and the modulus of rupture of SFR(H)C showed better results than the previous equations examined in this study in terms of not only accuracy but also safety/reliability.
Identifying the Significance of Factors Affecting Creep of Concrete: A Probabilistic Analysis of RILEM Database
Adam, Ihab ; Taha, Mahmoud M. Reda ;
International Journal of Concrete Structures and Materials, volume 5, issue 2, 2011, Pages 97~111
DOI : 10.4334/IJCSM.2011.5.2.97
Modeling creep of concrete has been one of the most challenging problems in concrete. Over the years, research has proven the significance of creep and its ability to influence structural behavior through loss of prestress, violation of serviceability limit states or stress redistribution. Because of this, interest in modeling and simulation of creep has grown significantly. A research program was planned to investigate the significance of different factors affecting creep of concrete. This research investigation is divided into two folds: first, an in-depth study of the RILEM creep database and development of a homogenous database that can be used for blind computational analysis. Second: developing a probabilistic Bayesian screening method that enables identifying the significance of the different factors affecting creep of concrete. The probabilistic analysis revealed a group of interacting parameters that seem to significantly influence creep of concrete.
Comparative Study for Grinding of Two Cement Clinkers
Ibrahimi, Soumaya ; Jamaa, Nejib Ben ; Mliki, Khaoula ; Bagane, Mohamed ;
International Journal of Concrete Structures and Materials, volume 5, issue 2, 2011, Pages 113~117
DOI : 10.4334/IJCSM.2011.5.2.113
The purpose of this work is the comparative study for grinding of two cement clinkers. X-ray fluorescence, physical and granulometric tests and optical microscopy were used to characterize the clinkers. Also grinding tests were carried out for ten samples to determine the parameters influencing grindability of its clinkers. The results of calculation of the energies of grinding according to the law developed by Von Rittinger and the study of the microstructure of the two clinkers shows good agreements. Indeed, frequent clusters of belite which indicate a lack of uniformity and fineness have an effect on lowering the grindability. The obtained analyses and the results enabled us to interpret the granulometry and the microstructure of clinker to control quality and resistance.
Effect of Slag Grade and Cement Source on the Properties of Concrete
Becknell, Natalie Peterson ; Hale, William Micah ;
International Journal of Concrete Structures and Materials, volume 5, issue 2, 2011, Pages 119~123
DOI : 10.4334/IJCSM.2011.5.2.119
Presented in the paper are findings of a project that examined the effect of slag grade and cement source on the performance of concrete mixtures. Slag cement contents were 20, 40, and 60 percent of the total cementitious material content. Two grades of slag cement were examined (Gr. 100 and Gr. 120) along with two sources of Type I cement. Compressive strength, durability, and permeability were measured. The results showed that the cement source affected the early age strength of the mixtures. At 28 days of age, mixtures containing Gr. 120 slag cement had higher compressive strengths than mixtures containing Gr. 100 slag cement, but by 90 days of age, the trend reversed. As for the chloride ion penetrability, mixtures cast with Gr. 100 slag cement passed fewer coulombs at 28 and 90 days of age than similar mixtures containing Gr. 120 slag. Mixtures containing Gr. 120 slag had the greatest durability factors.
Tests on Cementless Alkali-Activated Slag Concrete Using Lightweight Aggregates
Yang, Keun-Hyeok ; Mun, Ju-Hyun ; Lee, Kang-Seok ; Song, Jin-Kyu ;
International Journal of Concrete Structures and Materials, volume 5, issue 2, 2011, Pages 125~131
DOI : 10.4334/IJCSM.2011.5.2.125
Five all-lightweight alkali-activated (AA) slag concrete mixes were tested according to the variation of water content to examine the significance and limitation on the development of cementless structural concrete using lightweight aggregates. The compressive strength development rate and shrinkage strain measured from the concrete specimens were compared with empirical models proposed by ACI 209 and EC 2 for portland cement normal weight concrete. Splitting tensile strength, and moduli of elasticity and rupture were recorded and compared with design equations specified in ACI 318-08 or EC 2, and a database compiled from the present study for ordinary portland cement (OPC) lightweight concrete, wherever possible. Test results showed that the slump loss of lightweight AA slag concrete decreased with the increase of water content. In addition, the compressive strength development and different mechanical properties of lightweight AA slag concrete were comparable with those of OPC lightweight concrete and conservative comparing with predictions obtained from code provisions. Therefore, it can be proposed that the lightweight AA slag concrete is practically applicable as an environmental-friendly structural concrete.
Experimental Study on the Characteristics of Rapid Chilled Converter Slag by Watering
Lee, Keun-Jae ; Yoo, Seung-Yeup ; Koo, Ja-Sul ; Cho, Bong-Suk ; Lee, Hoon-Ha ;
International Journal of Concrete Structures and Materials, volume 5, issue 2, 2011, Pages 133~137
DOI : 10.4334/IJCSM.2011.5.2.133
In this study, a physical and chemical properties analysis was conducted for PCSP to evaluate properties of its materials and, for comparison purpose, was also conducted for CSP. The result of experiment confirmed improvement of iron recovery rate due to introduction of rapid water-cooling equipment and greater density of exterior and interior structure through SEM observation and porosity measurement. Also, SEM, XRD and DSC-TGA analysis showed that content of f-CaO in PCSP was minuscule so it was decided that problems of material stability including f-CaO-caused bulging failure, which has been problematic, can be solved.