• Proceedings of the Korea Concrete Institute Conference
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• 1995.04a
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• pp.42-47
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• 1995

The flow properties of xoncrete depend on form of fine aggregate, the ratio of voides of fine aggregate and cement paste So, in this study, investigated for the improvement of rheology properties on mortar and paste replaced by Zeolite $\circled1$ The slump flow have to do with correlation on yielding value of mortar respectirely. $\circled2$The increase ratio of strength Mortar and paste 10% replaced by Zeolite was presented significently but the slump flow was decteased stiffly as the increase of plastic viscosity at the ratio of replacement over 10%

• Magazine of the Korean Society of Agricultural Engineers
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• v.45 no.7
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• pp.11-19
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• 2003

In this study, unsaturated polyester resin, artificial lightweight coarse aggregate, artificial lightweight fine aggregate, heavy calcium carbonate and steel fiber were used to produce a steel fiber-reinforced lightweight polymer concrete with which mechanical properties were examined. Results of this experimental study showed that the flexural strength of unnotched steel fiber-reinforced lightweight polymer concrete increased from 8.61 to 13.96 MPa when mixing ratio of fiber content increased from 0 to 1.5%. Stress intensity factors($K_{IC}$) increased with increasing fiber content ratio while it did not increase with increasing notch ratio. Energy release rate ($G_{IC}$) turned out to depend upon the notch size, and it increased with increasing steel fiber content.

• Computers and Concrete
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• v.5 no.6
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• pp.559-572
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• 2008

The effects of fly ash and superplasticizer (SP) on workability of concrete are quite difficult to predict because they are dependent on other concrete ingredients. Because of high complexity of the relations between workability and concrete compositions, conventional regression analysis could be not sufficient to build an accurate model. In this study, a workability model has been built using artificial neural networks (ANN). In this model, the workability is a function of the content of all concrete ingredients, including cement, fly ash, blast furnace slag, water, superplasticizer, coarse aggregate, and fine aggregate. The effects of water/binder ratio (w/b), fly ash-binder ratio (fa/b), superplasticizer-binder ratio (SP/b), and water content on slump were explored by the trained ANN. This study led to the following conclusions: (1) ANN can build a more accurate workability model than polynomial regression. (2) Although the water content and SP/b were kept constant, a change in w/b and fa/b had a distinct effect on the workability properties. (3) An increasing content of fly ash decreased the workability, while raised the slump upper limit that can be obtained.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.69-74
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• 2003

This study evaluated durability through measurement of substituted test piece's pH degree and experiments of neutralization. Comparing and evaluating cared test piece's pH degrees which we got before the neutralization and after the neutralization. After evaluating neutralization depth through neutralization, evaluating neutralization properties by Fly Ash replacement ratio. pH degree was decreased by cement replacement ratio of Fly Ash. And in the case of substitution of the same amount of Fly Ash, fine aggregate replacement ratio was increased. When the test piece, which had been cared in high temperature, was promoted to neutralization, Among the test piece which was replaced with Fly Ash 40%, the test piece which has high rate of fine aggregate proved opposition of neutralization Through the test, Ⅰ summarized that the test piece cared in high temperature was mostly effected by compress strength, the test piece cared in low temperature was mostly effected by pH degree.

• Journal of The Korean Society of Agricultural Engineers
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• v.51 no.1
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• pp.21-26
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• 2009

This study was performed to evaluate the physical and mechanical properties of concrete using waste activated carbon. Materials used were ordinary portlant cement, crushed coarse aggregate, natural fine aggregate, waste activated carbon, and superplasticizer. The substitution ratios of waste activated carbon were 0,1,2,3,4,5,6,7,8,9 and 10%. The unit weight was decreased and water absorption ratio was increased with increasing the waste activated carbon content, respectively. When the substitution ratio of waste activated carbon was 3%, compressive strength, flexural strength and dynamic modulus of elastisity were more higher than that of the ordinary portland cement (OPC), and it was decreased with increasing the waste activated carbon content, respectively. The most effective contents of waste activated carbon was 2% in performance and 4% in practical use Accordingly, waste activated carbon can be used for concrete material.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05b
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• pp.41-44
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• 2005

The aim of this study is to develop experimentally ultra high-strength concrete with compressive strength over 100MPa with current materials by important factors to influence the compressive strength of concrete. There are so many factors which influence the manufacturing of ultra high-strength concrete. But the experimental factors selected in this study are the sand aggregate ratio, the silica fume replacement ratio, the type of aggregate, the type of superplasticizer, the fiber mixing ratio. The results of this experimental study show that it is possible to applicate in the field.

• Journal of the Korea Institute of Building Construction
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• v.3 no.3
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• pp.91-97
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• 2003

At present, the antiwashout underwater concretes are used as popular construction materials in European countries, the United States and Japan. The water-soluble polymers in the antiwashout underwater concretes provide excellent segregation or washout resistance, self-compaction and self-leveling property to the concretes. The purpose of this study is to recommend to optimum mix proportions of antiwashout underwater concretes according to compressive strength of 300kgf/$\textrm{cm}^2$ to 500kgf/$\textrm{cm}^2$. The antiwashout underwater concretes are prepared with various unit cement content, unit water content, sand-aggregate ratio, unit antiwashout agent and superplasticizer content. And they are tested for flowability, and compressive strength. From the test results, it is possible to recommend the optimum mix proportions of antiwashout underwater concretes according to compressive strengths within the range of 300kgf/$\textrm{cm}^2$ to 500kgf/$\textrm{cm}^2$.

• Journal of the Korea institute for structural maintenance and inspection
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• v.5 no.3
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• pp.123-130
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• 2001

The purpose of this study is to suggest the non-destructive equation for the estimation of concrete strength by ultrasonic pulse velocity at the Age of 28day compressive strength of $600{\sim}1000kg/cm^2$. For this purpose, selected test variables were water-hinder ratio, replacement ratio of silica fume, binder content, maximum size of coarse aggregate and sand-aggregate ratio. From the results, the average increase or decrease of ultrasonic pulse velocity is 61m/sec for each 1% of moisture content. And the correlation equation between the ultrasonic pulse velocity and the compressive strength of concrete is as follows. $F_c=896.3V_p-3514$ ($R^2$ = 0.81) where, $F_c$ : compressive strength($kgf/cm^2$), $V_p$ : ultrasonic velocity(km/sec).

• Journal of the Society of Disaster Information
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• v.6 no.1
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• pp.78-90
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• 2010

Exposure to the outside, the concrete is differential moisture distribution depending on the depth. Such a differential moisture distribution causes the differential drying shrinkage in concrete structures. This thesis is researched to compare the shrinkage of lightweight concrete depending on depth to normal concrete. It is used artificial lightweight aggregate which has 20% of pre-absorb value by lightweight concrete. When water-binder ratio is 30%, average shrinkage of lightweight concrete section decreased than normal concrete, but differential shrinkage of lightweight concrete section increased. However water-binder ratio is 40% and 50% average shrinkage and differential shrinkage of lightweight concrete section decreased than normal concrete.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10a
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• pp.11-30
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• 2000

Structural properties of reinforced concrete, such as bond and shear strength, that depend on the tensile properties of concrete are much lower for high-strength concrete than would be expected based on relationships developed for normal-strength concretes. To determine the reason for this behavior, studies at the University of Kansas have addressed the effects of aggregate type, water-cementitious material ratio, and age on the mechanical and fracture properties of normal and high-strength concretes. The relationships between compressive strength, flexural strength, and fracture properties were studied. At the time of test, concrete ranged in age from 5 to 180 days. Water-cementitious material ratios ranged from 0.24 to 0.50, producing compressive strengths between 20 MPa(2, 920 psi) and 99 MPa(14, 320psi). Mixes contained either basalt or crushed limestone aggregate, with maximum sizes of 12mm(1/2in). or 19mm(3/4in). The tests demonstrate that the higher quality basalt coarse aggregate provides higher strengths in compression than limestone only for the high-strength concrete, but measurably higher strengths in flexure, and significantly higher fracture energies than the limestone coarse aggregate at all water-cementitious material ratios and ages. Compressive strength, water-cementitious material ratio, and age have no apparent relationship with fracture energy, which is principally governed by coarse aggregate properties. The peak bending stress in the fracture test is linearly related to flexural strength. Overall, as concrete strength increases, the amount of energy stored in the material at the peak tensile load increases, but the ability of the material to dissipate energy remains nearly constant. This suggests that, as higher strength cementitious materials are placed in service, the probability of nonductile failures will measurably increase. Both research and educational effort will be needed to develop strategies to limit the probability of brittle failures and inform the design community of the nature of the problems associated with high-strength concrete.