• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.6
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• pp.144-151
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• 2023

In this study, a database was established by collecting experimental results on various concrete mixtures subjected to freeze-thaw cycles, based on which an artificial neural network-based prediction model was developed to estimate durability resistance of concrete. A regression analysis was also conducted to derive an equation for estimating relative dynamic modulus of elasticity subjected to freeze-thaw loads. The error rate and coefficient of determination of the proposed artificial neural network model were approximately 11% and 0.72, respectively, and the regression equation also provided very similar accuracy. Thus, it is considered that the proposed artificial neural network model and regression equation can be used for estimating relative dynamic modulus of elasticity for various concrete mixtures subjected to freeze-thaw loads.

• Geomechanics and Engineering
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• v.37 no.1
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• pp.85-95
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• 2024

This study investigates the influence of nano-silica and basalt fiber content, curing duration, and freeze-thaw cycles on the static and dynamic properties of soil specimens. A comprehensive series of tests, including Unconfined Compressive Strength (UCS), static triaxial, and dynamic triaxial tests, were conducted. Additionally, scanning electron microscopy (SEM) analysis was employed to examine the microstructure of treated specimens. Results indicate that a combination of 1% fiber and 10% nano-silica yields optimal soil enhancement. The failure patterns of specimens varied significantly depending on the type of additive. Static triaxial tests revealed a notable reduction in the brittleness index (IB) with the inclusion of basalt fibers. Specimens containing 10% nano-silica and 1% fiber exhibited superior shear strength parameters and UCS. The highest cohesion and friction angle were obtained for treated specimens with 10% nano-silica and 1% fiber, 90 kPa and 37.8°, respectively. Furthermore, an increase in curing time led to a significant increase in UCS values for specimens containing nano-silica. Additionally, the addition of fiber resulted in a decrease in IB, while the addition of nano-silica led to an increase in IB. Increasing nano-silica content in stabilized specimens enhanced shear modulus while decreasing the damping ratio. Freeze-thaw cycles were found to decrease the cohesion of treated specimens based on the results of static triaxial tests. Specimens treated with 10% nano-silica and 1% fiber experienced a reduction in shear modulus and an increase in the damping ratio under freeze-thaw conditions. SEM analysis reveals dense microstructure in nano-silica stabilized specimens, enhanced adhesion of soil particles and fibers, and increased roughness on fiber surfaces.

• Journal of Korean Tunnelling and Underground Space Association
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• v.22 no.1
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• pp.121-133
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• 2020

Globally, the frequency and intensity of abnormal climate events are increasing. Since this can directly damage lives and property, it is important to establish and implement an appropriate maintenance strategy in response to abnormal weather. Facilities built in cold regions where cold wave or heavy snow occurs frequently can be more damaged by freeze-thaw than facilities located in other regions. However, there are no clear criteria for quantitatively identifying the damage of freeze-thaw and how to cope with it. Therefore, based on the results of indoor freezing tests, the freezing conditions considering regional climate characteristics were selected as one day at -14℃, two days at -7℃ or three days at -5℃. As a result, it was confirmed that they were in the freeze-thaw environment in order of Daegwallyeing (8.3 times), Cheorwon (5.3 times) and Taebeak (4.9 times) in Gangwon region. Through this study, the evaluation criteria of freeze-thaw of road tunnels were newly proposed. The freeze-thaw evaluation criteria of the road tunnel presented in this study can be used for the quantitative evaluation and maintenance strategy of tunnels in cold regions.

• Journal of the Korean Ceramic Society
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• v.27 no.3
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• pp.437-443
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• 1990

The resistivity of cement paste and mortar for freezing and thawing was investigated for densifying the structure of cement paste and mortor, slag, diatomaceous earth and fly ash as blending materials and superplasticizer were used, and air entraining agent was added to absorb the volume expansion by freezing and thawing reaction. And then the specimens were subjected to freeze-thaw in water. When both of air entraining agent and superplasticizer as additives were mixed to specimens, their freeze-thaw resistance was enhanced by the air entraining effect and the water reduction effect. When 4% of slag were added to cement, freeze-thaw resistance was especially excellent. In addition, it was found that the specimens with blending materials were more influenced by curing periods than those without admixture. It is assumed that the curing periods contribute to exibit the potential hydraulicity and pozzolanic reactivity of blending materials and to densify their texture.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.04a
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• pp.123-128
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• 1998

Currently the study on the effective use of the fly ash is concentrated as construction materials, which is by product of electric power generating plants. Fly ash, therefore, can be used as concrete admixture for the purpose of not only increasing the concrete quality but also of utilizing materials. Within the country it is not easy to use fly ash for the construction purpose because the properties of fly ash are varied due to the use of different raw ores in the various power plants. And little previous construction experiments and the basic experiments about the formation of bubbles are performed. In this study the water-cement ratio is varied in 3 different values and compressive strength is measured and freeze-thaw experiments are preformed to establish the relationships between water-cement ratios and the durability. And also for each batch of different water-cement ratio fly ash is substituted 10%, 20% and 30% of cement and concrete mixture the admixture and the formation of bubbles and also freeze-thaw resistance.

• Journal of the Korea institute for structural maintenance and inspection
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• v.1 no.2
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• pp.123-130
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• 1997

The effect of experimental factors on the Freeze-Thaw durability in the High Strength Concrete has been analyzed and investigated with [DESIGN of EXPERIMENT: L16). The Experimental parameters included the type of aggregate and mixer, the conditions of aggregates, and the difference of mixing temperature, procedure and placing, etc. It is aim of this study to provide the fundamental data on the effect of various factors on the frost resistance of high strength concrete for the practical use and research data accumulation of durability inspection. The results of this experiment indicate that the freeze-thaw durability of high strength concrete is markedly affected by the coarse aggregate source, mixing temperature and curing conditions.

• Proceedings of the Korea Concrete Institute Conference
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• 1990.10a
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• pp.145-150
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• 1990

In order to discuss the freeze-thaw durability of FRC and mechanical properties by the fiber types of FRC, experimental studies of FRC were carried out. The kinds of fiber used which are in CFRC are PAN-based and Pitch-based carbon fiber and in GFRC are alkali-resistance glass fiber. To examine the effects of the kinds, types (continuous fiber and Tow, Belt, Cloth) and contents of fiber and matrices, the following three methods CFRC and GFRC, Air cured, Water cured and Autoclaved CFRC and GFRC were tested. According to the test results, the flexural, tensile strength and toughness of FRC were remarkably influenced by types of fiber and addition of condensed silica fume. Also, freeze-thaw resistance of FRC was considerably improved in comparision to conventional mortar.

• KCI Concrete Journal
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• v.11 no.3
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• pp.29-43
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• 1999

The effects of superplasticizers on fresh and hardened concrete were investigated. The experimental program included tests on the workability and slump loss, bleeding, setting time, air content, compressive, tensile and flexural strength, permeability, shrinkage, freeze-thaw durability and creep deformation. Properties of superplasticized concrete were compared with those of conventional and base concretes. Superplasticizers were observed to have an appreciable fluidifying action in fresh concrete. They permitted a significant water reduction while maintaining the same workability. Bleeding of superplasticized concrete was much lower than that of conventional concrete of the same consistency. This indicates that the use of superplasticizers did not affect the tendency of segregation of fresh concrete. The compressive, tensile, and flexural strengths of superplasticized concrete were significantly higher than those of conventional concrete. The permeability and drying shrinkage and creep of superplasticized concrete were less than those of conventional concrete, but there were no significant differences between base and superplasticized concrete. Compared with base concrete, non-air-entrained superplasticized concrete had slightly higher freeze-thaw durability. and superplasticized concrete with an appropriate amount of entrained air Eave even better resistance to freezing and thawing.

• KCI Concrete Journal
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• v.11 no.3
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• pp.65-77
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• 1999

A portland cement was reinforced by incorporating carbon fiber(CF), silica powder, and impregnating the pores with styrene monomers which were polymerized in situ. The effects of type, length, and volume loading of CF, mixing conditions, curing time and, curing conditions on mechanical behavior as well as freeze-thaw resistance and longer term stability of the carbon-fiber reinforced cement composites (CFRC) were investigated. The composite Paste exhibited a decrease in flow values linearly as the CF volume loadings increased. Tensile, compressive, and flexural strengths all generally increased as the CF loadings in the composite increased. Compressive strength decreased at CF loadings above approx. 3% in CFRC having no impregnated polymers due to the increase in porosity caused by the fibers. However, the polymer impregnation of CFRC improved all the strength values as compared with CFRC having no Polymer impregnation. Tensile stress-strain curves showed that polymer impregnation decreased the fracture energy of CFRC. Polymer impregnation clearly showed improvements in freeze-thaw resistance and drying shrinkage when compared with CFRC having no impregnated polymers.

• Geomechanics and Engineering
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• v.29 no.3
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• pp.349-357
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• 2022

Abnormal climate events are occurring frequently around the world. In particular, cold waves and heavy snow lead to damage and deterioration of facilities, which can cause loss of life or property damage, such as shortening the lifespan of facilities. Therefore, it is very important to prepare an appropriate maintenance system and to establish a strategy to cope with abnormal weather conditions. In this study, laboratory freezing experiments were performed to analyze the freeze-thaw characteristics affecting the tunnel concrete lining, and heat flow analysis was carried out based on the test results. Based on these experimental and theoretical analysis results, quantitative freeze-thaw evaluation criteria for tunnel concrete linings were proposed.