• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.905-908
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• 2008

The existing concrete using ordinary portland cement has difficult in earth strength. so our study proceeded in using the micro cement. the result of experiment is follow that strength of micro cement was hard better than ordinary portland cement in early strength but flow of ordinary portland cement was better than micro cement. when OPC and MC mixed by fly-ash, flow degree is increased because of ball baring. fly-ash type wicked in early strength but flyash type hard than 28days strength of OPC. flow of GBFS is decreased, early strength is increased. when fly-ash mixed in MC, it was wicked strength.

• Journal of the Korean Geotechnical Society
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• v.26 no.9
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• pp.47-58
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• 2010

This paper presents the injection efficiency of 2.0 shot system which was verified by strength and injection time. In order to perform this study, laboratory model tests and field tests are carried out. The laboratory model tests consist of the test of injection time for verifying the injection ratio, and the tests of homo-gel and sand-gel strengths for estimating the characteristic of strength. It is found that the injection ratio of 1:2 shows the best seepage into the ground. The results of the strengths are also larger than other injection ratio. The large strength will also be expressed by field tests at construction site.

• Cement Symposium
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• no.5
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• pp.88-93
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• 1977

시멘트 입도는 수화반응 속도에 밀접한 관계가 있으며 이로 인한 강도 발현 및 제반 물리특성에 크게 기여한다. 따라서 제품관리에 Blaine 및 sieve test로서 분말도를 check하고 있는바 이 분말도가 cement 물리특성에 미치는 영향을 실험실적으로 검토하였다.

• Journal of the Korea Institute of Building Construction
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• v.16 no.5
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• pp.405-412
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• 2016

In order to examine the possibility of practical use of concrete at low-temperature environment using high early strength cement with cold resistance admixture, an experimental study on workability, freezing temperature and compressive strength of the mortar with different types of anti-freezer, water reducing agent and accelerator for freeze protection at low-temperature were evaluated. Compressive strength was increased in use of anti-freezer, especially SN anti-freezer was higher than CN anti-freezer. 0min flow was increased, the 20min flow was decreased. And 20min flow was improved in use of FR, RT water reducing agent. CF, LS accelerator for freeze protection, regardless of the type of water reducing agent, compressive strength was increased.

• Journal of Life Science
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• v.26 no.1
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• pp.129-139
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• 2016

Exercise increases the expression and interaction of major neurotrophic factors such as brain-derived neurotrophic factor (BDNF), insulin-like growth factor-1 (IGF-1), and vascular endothelial growth factor (VEGF) at both central and peripheral tissues, which contributes to improved brain and neural plasticity and cognitive function. Previous findings have been to understand the effect of light or moderate intensity aerobic exercise on neurotrophic factors and cognitive function, not that of high intensity aerobic exercise. However, recent findings suggest that high intensity interval training is a safe, less time-consuming, efficient way to improve cardiorespiratory fitness and weight control, thus American College of Sport Medicine (ACSM)’s guidelines for exercise prescription for various adult populations also recommend the application of high intensity interval training to promote their overall health. High intensity interval training also enhances the expression of BDNF, IGF-1, and VEGF at the brain and peripheral tissues, which improves cognitive function. Increased frequency of intermittent hypoxia and increased usage of lactate as a supplementary metabolic resource at the brain and neural components are considered a putative physiological mechanism by which high intensity interval training improves neurotrophic factors and cognitive function. Therefore, future studies are required to understand how increased hypoxia and lactate usage leads to the improvement of neurotrophic factors and what the related biological mechanisms are. In addition, by comparing with the iso-caloric moderate continuous exercise, the superiority of high intensity interval training on the expression of neurotrophic factors and cognitive function should be demonstrated by associated future studies.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.6
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• pp.720-727
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• 2017

This study determined the optimum mix proportions for volcanic-ash-based geopolymer by analyzing the flow, setting time, and compressive strength. $Na2SiO_3$ and NaOH were used as alkali activators, and NaOH concentrations of 2, 4, 6, and 8M were used for different experimental cases. The A/B ratios examined were 0.25, 0.3, 0.35, 0.4, and 0.45, and the ratios of volcanic ash to blast furnace slag binder were 7:3, 6:4, and 5:5. In the experiment, the flow and setting time tended to decrease and the compressive strength increased as the molarity of NaOH in the geopolymer increased. The optimum molarity of NaOH was determined to be 4M. As the A/B ratio increased, the setting time decreased and the compressive strength increased. The most advantageous A/B ratio for the setting time and strength was 0.35. Increasing the ratio of volcanic ash resulted in a longer setting time and lower compressive strength. The optimum binder ratio was chosen as 6:4 based on the setting time and compressive strength. Thus, 4M of NaOH, an A/B ratio of 0.35, and binder ratio of 6:4 are considered as the proper parameters for the volcanic-ash-based geopolymer.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.837-840
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• 2008

This study was achieved experiment to evaluate effect on fluidity and strength development ratio by slag replacement ratio to $40{\sim}100MPa$ HSC(High Strength Concrete) containing blast furnace slag(GGBS) and fly-ash(FA). Also it was suggested that most suitable replacement ratio of GGBS is effect by strength. The mix plan of concrete used in an experiment was used to the GGBS replacement ratio of 0, 12, 25% as the cement materials, and fly ash was used equally by replacement ratio 15%. According to test results, for use GGBS with fly ash as binder, slump of GGBS replacement ratio 25% is the most superior in 40MPa series, and appeared by thing which slump flow of GGBS 12% is the most superior in 60, 80MPa's series. The other side, was expressed that fluidity is excellent by FA replacement ratio 15% in 100MPa series. In the case of compressive strength 40MPa, it was exposed that the strength revelation is effect in until the GGBS principal parts ratio increases by replacement ratio 25%. Also, it was exposed that GGBS mixing ratio more than replacement ratio 25% is not since fitness in high strength concrete more than 100MPa.

• Cement Symposium
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• no.29
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• pp.50-57
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• 2002

• Journal of the Korean Geosynthetics Society
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• v.7 no.2
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• pp.1-5
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• 2008

The differential settlement on ordinary concrete buildings and paved roads are often occurred and which caused the failure of structure. The grouting method can be used for correcting the settlement of the structure. However, the grouting method has a disadvantage like that it takes a long time period to get a desired strength, and it is not a continuous in the phase of reinforced effect. In this paper, as an injecting material called GPCON to complement disadvantage, it is estimated about the characteristic that has a high-density expansion. With the changing of ground conditions and amount of injection, the change of physical strength on compression, the stability against chemical material are studied through the filming of SEM. The physical strength with compression is developed to high strength due to mixing with other material. It is not react with most of the material on chemical conditions except the component of alcohol. Through the SEM test. it is confirmed that the strength of material was increased as formation is being densified.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.321-324
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• 2008

Recently increasing interest in high-rise building around the world for more than 100 floor, the trend is the increasing use of high-strength and high-flowable concrete so as of productivity improvements and cost savings to improve the performance of the early strength development. This study is to reach the optimal combination by reviewing the performance of high-rise building which is required. The results show that $30.0{\sim}32.5%$ of W/B, $155㎏/m^3$ of unit water and FA10+SP10 is best properties for early strength of concrete.