• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.7 no.4
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• pp.26-30
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• 2011

In order to ship low & Intermediate level radioactive waste drums, which have been temporarily stored on site, to a disposal facility, their physical and chemical properties should be evaluated and proven to meet the acceptance guideline prior to their shipment. Ultrasonic velocity method, which has been used to estimate the strength of concrete, can be suggested to evaluate the compressive strength of solidified radioactive waste, which is one of the evaluated properties. The strength is estimated from acoustic velocity. However, a guided wave traveling along a drum is generated when applying ultrasonic method to the drum, and this makes it difficult to analyze the signal due to overlap between transmitted wave through the contents in drum and the guided wave. This paper reported feasibility of ultrasonic method to evaluate of the compressive strength of the solidified LLW. It is observed that the guide wave is greater than transmitted wave, and ultrasonic velocity could be estimated from transmitted wave signal arriving prior to the guided wave

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.919-924
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• 2001

The purpose of this study is to prepare the basic data for the development of building board with expanded perlite. Each paste was mixed with four levels of water cement ratio(30, 40, 50, 60%), and expanded perlite was substituted with four levels of substitutive ratio(20, 40, 60, 80%) for the each paste. The physical property, compressive strength, bending strength and thermal conductivity of each cement composite which is made through previously described method were analyzed and the result was as follow. In the case of 80 percent substitutive ratio, the cement composite had a mechanical defect which was resulted from lack of paste content. In the case of 40 and 60percent substitutive ratio, the cement composite had sufficient strength, light weight and low thermal conductivity for application to fire resisting board.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.731-736
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• 2003

Alkali silicate system has wide application to accelerating admixture for shotcrete, but it has several problems that decrease long-term strength and delay setting time. So alkali-free system was gradually focused on accelerating admixtures for shotcrete due to its environmental property. The aim of this study is to investigate effect of alkali-free accelerating admixtures on aluminum sulfate system containing diethanolamine or acrylic acid etc. The alkali-free accelerating admixture has better properties than silicate system accelerating admixtures on compressive strength and low pH as shotcrete. Especially, the compressive strength of alkali-free accelerating admixture containing diethanolamine was increased about 10% compared with the value of ordinary portland cement.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05a
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• pp.503-506
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• 2005

The purpose of this study was the Development of Retrofit Method for Beam Using Steel Plate Reinforced by Fiber Sheet.1. Additional reinforcements are not needed in the joining area of slab and beam web.2. Beam using carbon fiber reinforced plastic displays low effects in shearing effect.3. Beams reinforced steel plate by epoxy effect the capacities of strength. But the capacities of strength are rapidly reduced when adhesive surface be omitted. Thus details are needed in this case.4.Retrofit method for beam using steel plate reinforced by fiber sheet with epoxy rosin improves the capacities of strength and the initial stiffness, shows a large transformation since the maximum load likewise may be excellent to the shearing reinforcement.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2018.11a
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• pp.23-24
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• 2018

Reinforced concrete is a building material that is generally used in modern society. Also, reinforced concrete structures in high salinity environments have low durability due to corrosion of reinforcing bars due to infiltrated chlorine ions. Anion exchange resins have an ability to immobilize chlorine ions in the resin while releasing their anions. As a material, it has already been shown that it is possible to fix the chloride ion inside the cementitious material through the cement mortar experiment. The purpose of this study is to confirm the compressive strength of cement mortar using powdered anion exchange resin after powdering an anion exchange resin. In order to confirm the chloride ion fixation ability of the powder anion exchange resin, chlorine ion penetration resistance test was carried out.

• International Journal of Highway Engineering
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• v.7 no.2 s.24
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• pp.13-22
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• 2005

Using recycled aggregate from demolished concrete structures provides a peat opportunity fur conserving natural resources. In many parts of world, virgin aggregate deposits have been depleted, and transporting aggregates over long distances can be much more expensive than using a low-cost recycled aggregate. In Korea, about 7-million tons of concrete occurs annually, out of this, about 2-3 million tons are available for recycling. This study is to present the method of utilizing the recycled aggregate. The recycled aggregate concretes were made for compressive strength test, flexural strength test and fatigue test using w/c of 40, 50 and 60%. The replacing rates of recycled aggregate to virgin aggregate were 0, 25 and 50%. The purpose of this study is to compare the fatigue lift of recycled aggregate concrete with that of virgin aggregate concrete. It was shown that the fatigue life of recycled concrete was function of recycled aggregate replacement ratio and water cement ratio.

• Journal of the Korea Institute of Building Construction
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• v.15 no.2
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• pp.177-183
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• 2015

In this study, the thermal conductivity, physical and mechanical properties of lightweight aggregate concretes with hollow micro sphere(HMS) are experimentally examined as a basic research for the development of structural insulation concrete. As the results of this experiment, in the case of concrete mixed with HMS, the value of slump has been reduced, so it is found that the dosage of superplasticizer should be increased. As the replacement ratio of HMS increases, it has shown that the compressive strength is somewhat decreased due to the low interfacial adhesion strength of HMS. But the thermal conductivity is found to be greatly improved with the replacement ratio of HMS increases, the thermal conductivity of HMS shows the lower value of 68% at lightweight aggregate concrete and 32% of normal concrete. Also it is found that the compressive strength is decreased and thermal conductivity is increased as the water-cement ratio increases. The most outstanding for insulation performance is observed when using 20% of HMS and 50% of water-cement ratio.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.2
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• pp.87-93
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• 2018

The use of high-strength concrete in construction have been increasing steadily. However, high-strength concrete has a low water-binder ratio, and the problems such as cracks due to hydration heat and shrinkage during the hydration process at the early age. Recently, as a method to reduce the shrinkage of concrete, study of internal curing has carried out according to increasing about interest about it. In this study, the effect of compressive strength on the curing condition(drying, moist, water) was investigated by using artificial lightweight aggregate(LWA) in high strength and high volume mortar. As a result of autogenous shrinkage, the effect of shrinkage reduction was enhanced depending on the increasing of LWA replacement. According to the curing condition, the results of compressive strength showed the different trend. The compressive strength has increased on the drying and moisture condition and decreased on the water condition.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.1
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• pp.78-85
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• 2023

This study evaluates the performance of reinforced concrete columns using hybrid fiber sheets for structural behavior. The purpose of this method is to improve the load-bearing capacity of the reinforced structure by impregnating a hybrid fiber sheet, which is woven by arranging aramid and glass fibers uniaxially and attached to an aged concrete structure requiring reinforcement with epoxy. In particular, not only the weight reduction of the material obtained by using a fiber lighter than the steel material, but also the low-strength, high-toughness fiber element among the fibers used delays the brittle fracture of the high-strength, low-toughness fiber element. The low-strength, high-toughness fiber element among the fibers used delays the brittle fracture of the high-strength, low-toughness fiber element, resulting in weight reduction compared to steel. The study conducted structural tests on four specimens, with the hybrid reinforcement method and failure mode as main variables. Specimen size and loading conditions were chosen to be comparable with previous studies. The structural performance of the specimen was evaluated using energy dissipation capacity and ductility. Analysis shows that excellent results can be obtained with the hybrid fiber sheet reinforcement.

• Journal of the Korean Society for Advanced Composite Structures
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• v.6 no.2
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• pp.105-117
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• 2015

The purpose of this study is to develop a new seismic resistant method by using precast concrete wall panels for existing low-rise, reinforced concrete beam-column buildings such as school buildings. Three quasi-static hysteresis loading tests were experimentally performed on one unreinforced beam-column specimen and two reinforced specimens with L-type precast wall panels. The results were analyzed to find that the specimen with anchored connection experienced shear failure, while the other specimen with steel plate connection principally manifested flexural failure. The ultimate strength of the specimens was determined to be the weaker of the shear strength of top connection and flexural strength at the critical section of precast panel. In this setup of L-type panel specimens, if a push loading is applied to the reinforced concrete column on one side and push the precast concrete panel, a pull loading from upper shear connection is to be applied to the other side of the top shear connection of precast panel. Since the composite flexural behavior of the two members govern the total behavior during the push loading process, the ultimate horizontal resistance of this specimen was not directly influenced by shear strength at the top connection of precast panel. However, the RC column and PC wall panel member mainly exhibited non-composite behavior during the pull loading process. The ultimate horizontal resistance was directly influenced by the shear strength of top connection because the pull loading from the beam applied directly to the upper shear connection. The analytical result for the internal shear resistance at the connection pursuant to the anchor shear design of ACI 318M-11 Appendix-D except for the equation to predict the concrete breakout failure strength at the concrete side, principally agreed with the experimental result based on the elastic analysis of Midas-Zen by using the largest loading from experiment.