• Proceedings of the Korea Concrete Institute Conference
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• 2001.05a
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• pp.641-646
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• 2001

Generally, when Fly-Ash was used as replacement material of cement in concrete, it might occur retardation of setting and hardening. So, it is unable to use a large amount of Fly-Ash as replacement for cement. However, if it is used as replacement material of fine aggregate in concrete, we can use a large amount of Fly-Ash and settle a problem of natural-aggregate exhaustion. Furthermore, engineering properties of High Volume Fly-Ash Concrete Is better than that of plain concrete But, the larger Fly-Ash is replaced, the more fluidity of High Volume Fly-Ash Concrete decrease, because porous organization of Fly-Ash adsorb water and Superplasticizer. In this study, after appending additional water to High Volume Fly-Ash Concrete in proportion to weight of Fly-Ash, we intend to find proper ratio which doesn't affect strength and satisfy fluidity As a result of this study, it was found that fluidity of mortar with 25~28 percentage of additional water was satisfied with fluidity of plain mortar, and compressive strength of that was similar to plain mortar's

• Journal of the Korean Ceramic Society
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• v.39 no.12
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• pp.1164-1170
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• 2002

The effect of fly ash addition to the kaolin block has been investigated. The addition affected the firing temperature and physical properties such as water absorption and compressive strength. The starting materials were from korea natural resources and the fly ash were from the power plant using coal as fuel, containing free carbon of 8∼9 wt%. The starting natural materials were mixed with 5 different proportions of fly ash, pressed and then sintered at 1050, 1100, 1150 and 1200${\circ}C$. With sintering temperature, water absorption decreased and compressive strength increased. When specimens were sintered at the temperature lower than 1100${\circ}C$, water absorption increased and strength decreased with fly ash content. In contrast, when sintering was done at the temperature higher than 1150${\circ}C$, water absorption increased with fly ash content similarly but strength was improved.

• Journal of Mechanical Science and Technology
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• v.15 no.6
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• pp.804-812
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• 2001

A triboelectrostatic separation system for removing unburned carbon from coal fly ash is designed and evaluated. Fly ash from a coal-fired power plant is used as an accepted additive in concrete where it adds strength, sulfate resistance and reduced cost, provided acceptable levels of unburned carbon are maintained. Unfortunately, unburned carbon in coal fly ash absorbs some of other additives and reduces the concrete strength. This paper describes to investigate dry triboelectrostatic process to separate unburned carbon from coal fly ash and utilize it into economically valuable products. The laboratory-scale triboelectrostatic separation system consists of a particle feeding system, a tribocharger, a separation chamber, and collection systems. Particles of unburned carbon and fly ash can be imparted positive and negative surface charges, respectively, with a copper tribocharger due to differences in the work function values of the particles and the tribocharger, and can be separated by passing them through an external electric field. Results showed that fly ash recovery was strongly dependent on the electric field strength and the particle size. 70wt% of fly ash containing 6.5wt% of carbon contents could be recovered at carbon contents below 3%. The triboelectrostatic separation system showed a potential to be an effective method for removing unburned carbon from coal fly ash.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.1219-1224
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• 2001

In this study, concrete what plenty of fly ash used as binder is left in three condition humid condition($35^{\circ}C$), normal condition($20^{\circ}C$) and cold condition($5^{\circ}C$). Fly ash concrete is tested in fresh properties and early strength. The result of tests could give the decisive factor of form side's stripping time. The purpose of this study is presenting the stripping time data to help the construction work. The result of this study is below. 1. The plain concrete specimen in humid condition developed high strength before 5 days, then strength development is declined. 10 day strength of plain specimen is smaller than the normal condition specimen's. 2. The strength of the concrete which plenty of fly ash used is more developed than the concrete in normal condition. It says that fly ash concrete is useful in the humid condition. 3. As fly ash substitution rate is downsizing and outdoor temperature degree is low, form stripping times is getting shorter.

• Proceedings of the Korea Concrete Institute Conference
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• 1994.10a
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• pp.229-234
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• 1994

Various of batches of recycled concretes were produced with different rations of recycled aggregate (20% and 50%) and admixtures based on workable range of slump value and using a fixed w/c ration. Mechanical characteristics of the recycled concretes were evaluated. Test results showed that, in general, relatively high strength recycled concrete could be obtained using a plasticiser. The concrete using fly ash showed somewhat reduced strength, lower elastic modulus and relatively high strain, in general. However, the strength reduction ratio of the recycled concrete due to adding fly ash was relatively minor, compared with normal concrete. Since it has been known that the fly ash is used in place of cement and gives an improved long term strength, a further study may be warranted for a possibility of using fly ash without degrading the strength required.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.10a
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• pp.345-350
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• 1997

This paper describes an experimental study on the strength and flexural toughness of steel fiber reinforced concrete using fly ash. The fly ash contents were varied from 0% to 20% of cement weight to explore the effect of fly ash addition with steel fiber reinforced concrete. as the result, the tensile strength, flexural strength and flexural toughness were increased remarkably as steel fiber contents were increased to 2.0 vol.%. Also, the steel fiber reinforced concrete containing 10% fly ash developed the highest strength. In the same contents of steel fiber, the flexural toughness characteristics show excellent when fly ash contents were 10% and steel fiber contents were 1.5 vol%.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.85-88
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• 2006

This study describes the optimum mix proportion of the high strength and self-compacting concrete placed in main structures of LNG above tank. This concrete requires high strength level about $60{\sim}80MPa$, low hydration heat, balance between workability and consistency without vibrating in the actual work. For this purpose, low heat portland cement and fly ash are selected and design factors including water-binder ratio, replacement ratio of fly ash are tested. As experimental results, low heat portland cement shows lower the confined water ratio than another cement type and the optimum replacement ratio of fly ash in order to improve properties of the binder-paste shows 10% by cement weight considering test results of the confined water ratio$({\beta}p)$. Also, flowability of the high strength and self-compacting concrete by using fly ash about $10{\sim}20%$ is improved. The replacement ratio of fly ash 10% and water-binder ratio $25{\sim}27%$ are suitable to the design strength 80MPa and cost, In case of the design strength 60MPa, the replacement ratio of fly ash and water-binder ratio show 20% and $25{\sim}30%$ separately. Based on the results of this study, the optimum mix proportions of the high strength and self-compacting concrete will be applied to the construction of LNG above tank as a new type.

• Proceedings of the Korea Concrete Institute Conference
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• 1994.10a
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• pp.211-216
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• 1994

This study dealt with the properties for fly ash of conbined heat power plant and application for concrete industry. For this purpose, fly ash sampled Ulsan conbined heat power plant and analyzed for physical and chemical properties. As analyzed results of fly ash, contents of $SiO_ and Al_O_ $in the fly ash of Ulsan were less than those of Thermo-electric power plant(Boryuing), but contents of CaO were tem times as much as those of Boryung, because of these differences, it is expected that pozzolanic activity of concrete using fly ash of Ulsan will be different from another fly ash. Concrete specimens were tested to evaluate concrete preformance when 10 to 50 percent of the portland cement by weight in the concrete mix was replaced with fly ash of conbined heat power plant. As test results, workability and consideration in the fresh concrete were increased and concrete strength was showed more than 400kg/$\textrm{cm}^2$ for the required age. This study would be provided valuable data for the practical utilization of fly ash(conbined heat power plant). In the future, properties of fly ash concrete including long term strength, elapsed time, pozzolanic activity, modulus of elasticity, sulfate resistance, shrinkage, freeze-thaw durability and so on will be studied.

• Journal of the Korea Institute of Building Construction
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• v.3 no.3
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• pp.135-142
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• 2003

This study is for the great quantity use of fly-ash. For the producing of high volume concrete from the use of fly-ash, the method of replacement between bonding agents and fine aggregate by fly-ash was used at the same time. It was used that the adiabatic temperature rise of concrete about the mass member which had been produced by the method that was mentioned before, and the hydration heat of the core test pieces in concrete was measured. Also the core test pieces which were replaced with fly-ash was studied by the compressive strength's comparison between standard care test pieces and core test pieces. In the case of mass test pieces, hydration heat and the time to reach the highest temperature were decreased by an increase in replaced fly-ash's amounts of concrete. In addition, among the test pieces having the same amounts of concrete, the test pieces having more replaced amounts of fly-ash's fine aggregate showed higher hydration heat and the increased time to reach the highest temperature. Compressive strength was also increased by hydration heat's decrease according to fly-ash replacement. Replacement of fly-ash was more effective in high temperature environment.

• Journal of Industrial Technology
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• v.41 no.1
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• pp.1-6
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• 2021

Fly ash and silica fume belong to industry by-products that can be used to produce concrete. This study shows the model of a neural network to evaluate the strength development of blended concrete containing fly ash and silica fume. The neural network model has four input parameters, such as fly ash replacement content, silica fume replacement content, water/binder ratio, and ages. Strength is the output variable of neural network. Based on the backpropagation algorithm, the values of elements in the hidden layer of neural network are determined. The number of neurons in the hidden layer is confirmed based on trial calculations. We find (1) neural network can give a reasonable evaluation of the strength development of composite concrete. Neural network can reflect the improvement of strength due to silica fume additions and can consider the reductions of strength as water/binder increases. (2) When the number of neurons in the hidden layer is five, the prediction results show more accuracy than four neurons in the hidden layer. Moreover, five neurons in the hidden layer can reproduce the strength crossover between fly ash concrete and plain concrete. Summarily, the neural network-based model is valuable for design sustainable composite concrete containing silica fume and fly ash.