• Proceedings of the Korea Concrete Institute Conference
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• 2005.05b
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• pp.493-496
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• 2005

The Re-mi-con sludge water has been investigated because of environmental pollution and disposal cost. So, sludge water is partially reused as mixing water. However, if sludge water is reused too much that would influence the quality of concrete. KS specification limits the amount of sludge content up to 3$\%$ of cement weight. In this study, the effect of re-mi-con sludge on the characteristics of concrete is compared to raise the reuse ratio of re-mi-con sludge. From the test results, as blending ratio of re-mi-con sludge increases, workability is decreases. However, the re-mi-con sludge water have a minor effect on the strength development, the drying shrinkage and the resistance of freeze and thawing. Also, the existing model codes of drying shrinkage do not coincide with the test results of this study.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05b
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• pp.101-104
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• 2005

It analyzed the supply status of fine aggregate and find the point of issue related alternative fine aggregate through researches and interviews. The conclusions of the study are as follows. 1. Ready mixed concrete manufacture used crushed fine aggregate (15.5$\%$) and recycled fine aggregate (1.5$\%$) for alternatives aggregate than 1.3$\%$ in 1991. It is not allowed to use a recycled fine aggregate in ready mixed concrete, but they used it. 2. All alternative aggregate are satisfied the Korean Standard, But they showed low properties of mortar compared to when it replaced with natural fine aggregate. So, it is needed to make another special Korean Standard to use alternative aggregate in normal concrete by mixing method to recover the workability and compressive strength.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05b
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• pp.377-380
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• 2005

The objective of this study is to evaluate the physical properties of rapid-setting asphalt concrete grouting materials. This study investigates the fluidity, viscosity and compressive strength at 3-hour of grouting materials with various mixing ratio. From the test results, when the quantity of CSA is over about 30 $\%$, the compressive strength of 3-hour was satisfied a minimum requirement of 7 days in Japan. Also, the fluidity for the time to infiltrate into pore of the asphalt concrete are enough to be applied in construction field.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2018.11a
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• pp.179-180
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• 2018

Color concrete is produced by adding white portland cement and coloring agent. In Korea, colorant added to color concrete is expensive, durability evaluation in external environment is not verified and there is a tendency to avoid color concrete pouring. Red mud with a water content of 50% was prepared in liquid form using appropriate mixing water and additives for recycling as a coloring agent, the liquefied red mud manufactured was intended to show the possibility of using color concrete. In this paper, the application of red mud as an industrial by - product as a coloring agent for color concrete was investigated for the practical use of liquefied red mud by liquefying red mud and producing retaining wall block. As a result, it was found that all of the specifications stipulated in SPS-KCIC0001-0703 are satisfied.

• Journal of the Korea institute for structural maintenance and inspection
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• v.5 no.3
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• pp.153-162
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• 2001

This paper presents the fundamental study on rational manufacture of Ultra High Strength(VHS) concrete using industrial by-products as like silica fume, slag and fly ash. In this study, we had tested various mixing cases to manufacture the UHS concrete(target compressive strength : over $1,000kgf/cm^2$) which is easily workable (target slump flow : $60{\pm}10cm$). The main variables are studied: 1) to find the optimum replacement ratio of mineral admixture. 2) to find a rational water-binder ratio and a proper binder content. 3) to find the method for reduction of slump loss. From the test results, it is concluded that the rational mix design can be made by using 40% slag, 10% silica fume. We found that compressive strength of UHS concrete increases according to decreasing W/B ratio but in W/B ratio 18~20%, the difference is vague and the compressive strength does not necessarily increase according to increasing binder content over 700kg.

• Architectural research
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• v.23 no.1
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• pp.11-17
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• 2021

A concrete-filled circular steel tube beam was fabricated, and a bending test was performed to analyze its failure modes, displacement ductility, bending-shear strength, and load-central deflection relationship. For the bending test, the installation position of the shape memory alloy (SMA) inside and outside the double-skin steel tube was used, and the rebar installation position, the concrete strength, the mixing of fibers, and the inner-outer diameter ratio as the main parameters. The test results showed that the installation positions of the reinforcements inside and outside the double-skin steel tube and the inner-outer diameter ratio of the steel tube affected the ductility, maximum load, and failure mode. In general, the specimen made of general concrete with SMA installed outside and inside (OI) the double-skin steel tube showed the best results.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2022.04a
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• pp.53-54
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• 2022

This study is a basic study to establish the relationship between the conventional fluidity evaluation data of concrete and the rheology parameters. the slump flow and rheology parameters were measured according to the elapsed time after the concrete was mixed. The correlation between the slump flow and the rheology constant was analyzed and the effect of the elapsed time after concrete beating on the correlation between the two data was analyzed.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.11a
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• pp.101-102
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• 2021

The compressive strength of concrete is greatly affected by the temperature inside the concrete at the initial age immediately after pouring. The apparent activation energy of cement and the setting time of concrete are major factors influencing the development of compressive strength of concrete. This study measured the apparent activation energy and setting time according to the change in W/B for each mixing rate of Ground Granulated Blast-Furnace Slag (GGBFS). And after calculating the compressive strength prediction model, the accuracy of the prediction model was evaluated by comparing the predicted compressive strength and the compressive strength.

• Corrosion Science and Technology
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• v.6 no.4
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• pp.177-185
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• 2007

The purpose of this study is to evaluate freezing-thawing and surface scaling resistance in order to examine the frost durability of concrete in a chloride-inherent environment. The mixing design for this study is as follows: 3 water binder ratios of 0.37, 0.42, and 0.47; 2-ingredient type concrete (50% OPC concrete and 50% ground granulated blast-furnace slag), and 3-ingredient type concrete (50% OPC concrete, 15% fly ash, and 35% ground granulated blast-furnace slag). As found in this study, the decrease of durability was much more noticeable in combined deterioration through both salt damage and frost damage than in a single deterioration through either ofthese; when using blast-furnace slag in freezing-thawing seawater, the frost durability and surface deterioration resistance was evaluated as higher than when using OPC concrete. BF 50% concrete, especially, rather than BFS35%+FA15%, had a notable effect on resistance to chloride penetration and freezing/expansion. It has been confirmed that surface deterioration can be evaluated through a quantitative analysis of scaling, calculated from concrete's underwater weight and surface-dry weight as affected by the freezing-thawing of seawater.

• Journal of the Korea Institute of Building Construction
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• v.4 no.4
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• pp.71-77
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• 2004

Drying Shrinkage has much complexity as it has relations with both internal elements of concrete and external factors. Therefore, experiments on Concrete Drying Shrinkage are carried out in this study under simplified circumstances applying temperature & Humidity test chamber which enables constant temperature and humidity. Comparative analyses have been made respectively according to the consequences aiming at modelling for prediction of Concrete Drying Shrinkage and making out measures to reduce it. Strain Rate of Drying Shrinkage of concrete under the condition of dry air appears to rise by about 20%-30% in proportion as the temperature rises $5^{\circ}C$ when the humidity was held below 10% compared under the condition of dry temperature & Humidity test chamber. Strain Rate of Drying Shrinkage in pit sand concrete increased 20% higher than measured when in river sand under the condition of 90-day material age. A general formula with two variables is derived as follow ${\varepsilon}={\alpha}_1＋{\beta}_1x_1＋{\beta}_2x_2＋{\beta}_3x_1^2＋{\beta}_5x_2^2$. and also graphed in 3 dimensions, enabling to apply to actual design and predict Strain Rate of Drying Shrinkage in concrete. The results of prediction of Rate of Drying Shrinkage by Response Surface Analysis are as follows. The coefficient of correlation of Drying Shrinkage in Concrete was over 90%.