• Journal of the Korea Concrete Institute
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• v.13 no.2
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• pp.139-145
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• 2001

One of ways to make high-strength concrete is for the mix contain particles graded down to the finest size : this is achieved by the use of fly ash, silica fume which fills the spaces between the cement particle and between the aggregate and the cement particles. And, the mix needs a sufficient workability. This is achieved by the use of a superplasticizer. This study is to investigate frost resistance of high-strength concrete at early age, with ratio of tensile strength and recovery of compressive strength, when high-strength concrete is placed in cold climates. According to this study, it is necessary to ensure 4 % of air content, 5 kgf/$\textrm{cm}^2$ of tensile strength, at least, for frost resistance of high-strength concrete at early age.

• Journal of the Korean Geosynthetics Society
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• v.20 no.4
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• pp.133-140
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• 2021

There are few attempts to estimate the strength and stiffness of controlled low strength material (CLSM) using existing field-testing methods. The objective of this study is to evaluate the resilient modulus of CLSM by using the Light Weight Deflectometer (LWD) and investigate the relationships between the resilient modulus from LWD and the unconfined compressive strength (UCS) and secant modulus of elasticity from unconfined compressive test. Five CLSMs with different mix designs are used to evaluate the flowability and the stiffening of the CLSM in the flow and Vicat needle tests, respectively. To evaluate the early strength and stiffness characteristics, unconfined compressive tests are performed using the CLSM specimens cured for 1 and 7 days. LWD tests are carried out to estimate the resilient modulus of the CLSM specimens. The experimental results show that for the curing time of 1 day, the UCS and secant modulus of elasticity generally increase with the fast setting mortar content (FC). The CLSM specimen with the highest FC shows the significant increase in the UCS and secant modulus of elasticity along the curing time. Overall, the resilient modulus for the curing time of 1 day increases with the FC, while that for the curing time of 7days decreases with an increase in the FC. From the results, the linear relationships between the resilient modulus and UCS and secant modulus of elasticity are established.

• 공원문화
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• s.43
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• pp.22-23
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• 1989

날로 병들어가는 자연과 인간성의 건전한 회복을 촉구하는 일은 오늘의 당면한 우리의 과제입니다. 본지는 뜻있는 필진의 찬동을 얻어 이번호부터 본시리즈를 연재하게 되었습니다. 본회회원은 물론 전국애독자의 관심과 투고를 바라마지 않습니다.

• Journal of Industrial Convergence
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• v.18 no.1
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• pp.97-107
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• 2020

Since long ago, there has been a saying that "Drink water to quench thirst, drink alcohol to remove anguish and anxiety, and drink tea to recover from fatigue and refresh mind." Tea is really better for body and mind than water when it is drunken long and is valuable Jinda(眞茶) given by mother nature. In particular, curing tea reflecting characteristics of climate changes in all seasons helps in keeping health. Since tea contains the Yin-Yang system, which is a philosophical ideology of ancient people, old predecessors knew which tea they should brew and drink for curing in harmony with Yin and Yang. As a factor that influences component changes of tea, a complex interaction of heaven, earth and man is important and especially, mind of a person to handle tea is most important. Tea is a natural curing drink, which plays a role as a bridge between humans and nature.

• Proceedings of the Korea Concrete Institute Conference
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• 2010.05a
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• pp.333-334
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• 2010

In this paper, quality variations of commercially available anti-freezers manufactured in Korea are studied. This study is focused on the effect of the use of anti freezer on strength recovery of cement mortar under low curing temperature. As expected, regardless of types of anti freezer, the use of antifreezer protects the water from freezing under low curing temperature.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2019.11a
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• pp.73-74
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• 2019

In order to examine the chemical stabilization through DCG curing of cement paste exposed to high temperature environment, we produced a sample of 40% W/C cement paste and heated it for 180 minutes under the heating temperature of $800^{\circ}C$. The DCG curing time was 6, Three time conditions were divided into 12 and 18 hours. As a result of XRD analysis, Calcite ($CaCO_3$) was found in Theta 29.4, 40, and 46.5o. As the curing time increased, the peak of Calcite also increased, which is due to the increased reaction time with DCG. Therefore, Calcite produced through DCG curing seems to have stabilized chemically by filling the pores generated by heating.

• Journal of the Korea Concrete Institute
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• v.15 no.1
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• pp.43-51
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• 2003

Recently, to consider financial and constructive aspect usage of Admixture such as Blast-Furnace Slag and Fly-Ash, are increased. Also the use of cold-weather-concrete is increased. Blast-Furnace Slag, a by-product of steel industry, have many advantage to reduce the heat of hydration, increase in ultimate strength and etc. But it also reduces early-age strength, so it is prevented from using of Blast-Furnace Slag at cold-weather-concrete. In this study, for the purpose of increasing usage of Blast-Furnace Slag at cold-weather-concrete, it is investigated the strength properties of concrete subjected to frost damage for the cause of early age curing. The factors of this experience to give early frost damaged were Freezing temperature(-1, -10, $-15^{\circ}C$), Early curing age(0, 12, 24, 48hour), Freezing times(0, 12, 24, 48hour). According to this study, if early curing is carried out before haying frost damage, the strength of concrete used admixture, subjected to frost damage, is recovered. And that properties are considered, the effect of using admixture like blast-furnace-slag, is very high

• Proceedings of the Korean Institute of Building Construction Conference
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• 2019.05a
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• pp.103-104
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• 2019

The aim of the research is assessing the possibility of recovering the compressive strength of the mortar mixture replaced excessively high volume of blast furnace slag accidently. As a result of the experiment, in the case of compressive strength, painting sodium oxide showed higher compressive strength recovery effect than painting calcium oxide. As a curing temperature, 20℃ showed advanced result rather than 65℃. From the wet curing, the reaction was confirmed, deeper penetration depth was checked at 20℃ than 60℃ temperature. Therefore for the concrete mixture with excessively high volume of blast furnace slag, it is considered that painting sodium hydroxide and curing 20℃ can recover the compressive strength effectively.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2019.05a
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• pp.199-200
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• 2019

The purpose of the research is assessing the possibility of strength recovery for mortar added with accidently high amount of fly ash. For compressive strength at 28 day, the sample painted with sodium hydroxide showed higher compressive strength than the sample painted with calcium hydroxide. Regarding the curing conditions, the curing temperature 65℃ provided better conditions than the curing temperature 20℃ in aspect of solution penetration depth and reactivity of fly ash. In the case of drying after saturation, the case painted with sodium hydroxid 65℃ showed the clearest engrossing mark.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.6D
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• pp.579-586
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• 2012

The main objective of the research is to evaluate the laboratory performances of epoxy asphalt mixtures for long-span steel bridge decks. The aggregate gradations were recommended for field applications. The laboratory performance test results showed that the durability of epoxy asphalt mixtures was more noticeable than that of conventional ones. The structural analysis was conducted using resilient modulus and bond-shear test results. The analysis results revealed that just 9% out of total bond-shear stress was enough for the entire required bond-shear stress in the pavement system. The tensile stresses in the bridge decks were within limits compared to the laboratory test results from the Nanjing Grand Bridge in China. As a result, the laboratory performances of the epoxy asphalt mixtures for long-span steel bridge decks were better than those of conventional asphalt mixtures. However, the laboratory performance tests of epoxy asphalt mixtures for long-span steel bridge decks should be conducted precisely since the strengths of the mixtures are sensitive to the temperatures and curing times.