• The Korean Journal of Ceramics
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• v.6 no.3
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• pp.318-321
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• 2000

Most compressive strengths commonly used in the construction field are in a range of 240 to 300 kgf/$\textrm{cm}^2$ at 28 days. To get this rage of strengths, however, high-flowing concrete requires cementitious binders more than 400 to 450 kg/$\textrm{cm}^2$ for preventing segregation and sedimentation of aggregates. This amount of cementitious binder generates a large emission of excessive hydration heat, which may consequently induce harmful cracks in concrete structure. In order to reduce excessive hydration heat, thus, this paper aims at fabricating a high-flowing concrete under the condition that cement content is kept as low as 350kg/$\textrm{cm}^3$ by using viscose agents. In a parametric study, effects of cement types such as a ternary blended cement and Type V on he physical characteristics of high-flowing concrete were evaluated. In addition, the influence of viscosity was also investigated by applying two different viscose agents, one in a range of 6,000 to 10,000 cps and the others of 10,000 to 14,000 cps. In terms of chemical admixtures used in concrete mixture, the superplasticizer was Sulfonated Melamine-Formaldehyde Condensate with about 30,000 of molecular weight, and main component of viscose agent was HPMC (Hydroxy Propyl Methyl Cellulose). Slump flow was fixed at 50cm with different dosages of superplasticizer in weight.

• Magazine of the Korean Society of Agricultural Engineers
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• v.38 no.6
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• pp.74-82
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• 1996

In this study, the characteristics of antiwashout underwater concrete according to the using types of admixture were experimentally investigated. Especially, the comparison on the performance of seven types(CO-A, B, C, D, E, F, G) of the manufactured admixtures was carried out in the same mixing condition and proportions. Based on the results of experiments, the conclusions were summarized as follows : (1) The slump flow on most of specimens except by CO-F type were progressed very well. (2) In most of products, the measured values of suspensions, pH's and air contents were lower than their reference values. However, CO-B, CO-F and CO-G types exceeded the reference ones in suspension and pH. (3) The time lags between initial and final setting were about three hours in most of tests, however, the maximum difference of total setting time was ten hours in comparing with the admixture types. The unit weights were mostly lower than $2300kg/m^3$ and the compressive strengths cured by salt water were about 80% of the ones by fresh water. (4) Finally, in spite of some problems, most of the manufactured admixtures may be performed well their functions in antiwashout under-water concrete if the using quantities are properly controlled by the site experiments.

• Journal of the Korea Concrete Institute
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• v.11 no.4
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• pp.21-29
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• 1999

In this study, an experiment was performed to analyze the influence of water-cement ratio on the fundamental characteristics of antiwashout underwater concrete using blended sand (sea sand:river sand = 1:1). The water-cement ratio (45%, 50%, 55%, 60%), andtiwashout underwater agent contents (0.82%, 1.00%, 1.14% of water contents per unit volume of concrete), and superplasticizer contents (1.5%, 2.0%, 2.5% of cement contents per unit volume of concrete) were chosen as the experimental parameters. The experimental results show that the underwater segregation resistance, unit weight of hardening concrete and compressive strength were increased as the water-cement ratio decreased and as the antiwashout underwater agent contents increased. On the other hand, the flowability(slump flow) was increased to the 55% of the increase of water-cement ratio, however, it was decreased at the ratio of 60%. From this study, the antiwashout underwater concrete can potentially be used as a materials underwater work of ocean if the water-cement ratio and chemical admixture contents for the suitable balance between cost and performance are properly selected.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05b
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• pp.425-428
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• 2005

In this study, the experiment was carried out to investigate and analyze the strength properties and flowability of concrete using meta kaolin. The main experimental variables were water/binder ratio 40.0$\%$, water content 170kg/$m^{3}$ and mineral admixtures such as slag powder, silica fume and meta kaolin. According to the test results, the principle conclusions are summarized as follows. 1) The flowing property of concrete that uses meta kaolin appears to be the same to that of the silica fume concrete, but the slump flow that evaluates the compaction ability of concrete shows the most favorable performance. 2) The air content of the concrete that uses meta kaolin can be effectively controlled for the target performance in compliance with the use of AE agent. 3) When it comes to the strength of concrete that uses meta kaolin, the most favorable development of strength occurs when the replacement rate is 10$\%$, in case of the silica fume, and the slag power. In addition, as the replacement rate increases, so becomes the development of concrete strength favorable.

• Journal of the Korea Concrete Institute
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• v.14 no.3
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• pp.349-356
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• 2002

This research deals with the properties of fresh and hardened high-performance concrete(HPC) incorporating high-reactivity metakaolin(HRM). The properties of fresh and hardened state concrete were investigated included air content, slump flow, setting time, heat of hydration, compressive strength, resistance to chloride-ion penetration, abrasion and repeated freezing and thawing. The properties of the HRM concrete were also compared with those of the portland cement concrete and silica fume(SF) concrete. The laboratory test results indicate that HRM material can be used as a supplementary cementitious material to produce high-performance concrete.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2007.11a
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• pp.95-98
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• 2007

This study investigates the mechanical properties of the high strength concrete in the region of 80MPa corresponding to the temperature and fiber content change. For the properties of the fresh, slump flow is $600{\pm}100mm$, and air content is $3.0{\pm}1.0%$. They satisfy each targets, and there was no difference for the each fiber types. As the propertied of the hardened concrete, the compressive strength at 28 days is indicated over 80MPa, and they are similar to the change of the fiber types. The residual compressive strength in response to the temperature change of the NY, PP, and NY+PP fiber at $200^{\circ}C$ are increased by 115, 114, and 110% on the standard condition, and it is suddenly decreased at $400^{\circ}C$. They are decreased by 33, 19, and 16% on the standard condition at $800^{\circ}C$.

• Computers and Concrete
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• v.19 no.2
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• pp.121-126
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• 2017

This paper presents the effect of aggregate type on high temperature resistance of self-compacting mortars (SCM) produced with normal and lightweight aggregates like expanded perlite and pumice. Silica fume (SF) and fly ash (FA) were used as mineral additives. Totally 13 different mixtures were designed according to the aggregate rates. Mini slump flow, mini V-funnel and viscometer tests were carried out on the fresh mortar. On the other hand, bulk density, porosity, water absorption and high temperature tests were made on the hardened SCM. After being heated to temperatures of 300, 600 and $900^{\circ}C$, respectively, the tensile strength in bending and compressive strength of mortars determined. As a result of the experiments, the increase in the use of lightweight aggregate increased total water absorption and porosity of mortars. It is observed that, the increment in the usage of lightweight aggregate decreased tensile strength in bending and compressive strengths of mortar specimens exposed to high temperatures but the usage of up to 10% expanded perlite in mortar increased the compressive strength of specimens exposed to $300^{\circ}C$.

• Computers and Concrete
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• v.19 no.2
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• pp.203-210
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• 2017

The purpose of this paper is to evaluate the settlement of lightweight coarse aggregate of self-compacting lightweight concrete (SCLC) after placement of concrete on its final position. To investigate this issue, sixteen samples of concrete mixes were made. The water to cementitious materials ratios of the mixes were 0.35 and 0.4. In addition to the workability tests of self-compacting concrete (SCC) such as slump flow, V-funnel and L-box tests, a laboratory experiment was made to examine the segregation of lightweight coarse aggregate in concrete. Because of the difficulties of this test, the image processing technique of MATLAB software was used to check the segregation above too. Moreover, the fuzzy logic technique of MATLAB software was utilized to improve the clarity of the borders between the coarse aggregate and the paste of the mixtures. At the end, the results of segregation tests and software analyses are given and the accuracy of the software analyses is evaluated. It is worth noting that the minimum and maximum differences between the results of laboratory tests and software analyses were 1.2% and 9.19% respectively. It means, the results of image processing technique looks exact enough for estimating the segregation of lightweight coarse aggregate in SCLC.

• KCI Concrete Journal
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• v.11 no.3
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• pp.79-88
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• 1999

Most difficulties of inducing high fluidity on the concrete mixing design with a strength range of 210 to 240kg/$\textrm{cm}^2$ result from the segregation of aggregates due to the shortage of cementitious binders. To solve the problem, this study concentrated on finding the optimized amount of binder material which does not affect the concrete strength and is also economical. Also there were studies on the use of intermediate sized aggregates to avoid the gap-grading between coarse and fine aggregates so that the material segregation in high flowing concrete was and minimalized the fluidity and penetration capacity of the reinforcing bars was enhanced. Throughout the parametric study with respect to water/binder ratio. superplasticizer. replaceable mineral admixture, the size of coarse aggregate and mixing methods, the effect of each constituent on the characteristics of high flowing concrete could be observed. As a result or partially using stone powder or an intermediate class of aggregate (max. diameter 13mm) . it was fund that the fluidity of concrete significantly increased without material segregation and any change of compressive strengths. It was also proved in this study that proper mixing time and speed are significant factors influence the performence of high flowing concrete.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.449-452
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• 2006

In this study, recently, more highly effective construction materials are needed for a reasonable cause and economical structure system is required as the construction structures become more multi storied, large-sized and diversified. Also, the experiment was not carried out to investigate and analyzed the strength properties and flowability of ultra-high strength accroding to the types of mineral admixtures. Therefore, this is an experimental study to compare and analyze the influence of cementitious materials type on the fluidity and the strength properties of ultra-high strength concrete. For this purpose, it has decided to do the mix proportions of concrete according to the type of cementitious materials (fly ash, blsat furnace slag, silica fume, slag cement) and W/B(23.5, 27.5, 31.5%) has selected. And then we conducted an experiment to find out basic properties of the ultra-high strength concrete such as slump-flow, O-lot and the age of specimens(3, 7, 28, 56days) for compressive strength.