• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.05a
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• pp.229-230
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• 2023

In this study, the hydration heat differential method was applied to mass concrete structures, and the hydration heat analysis was compared and analyzed with on-site measurement results. The results showed that the temperature history measurements of mass concrete were managed at a difference of 8.4 ℃, and although there was some deviation in thermal stress, a similar trend was observed. Consequently, it was determined that the thermal stress on the surface of mass concrete is less than its tensile strength, which would prevent the occurrence of thermal cracks.

• Proceedings of the Korea Information Processing Society Conference
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• 2008.05a
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• pp.111-114
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• 2008

본 논문에서는 고유영상 추출에 기반을 둔 동물표현의 수화인식 기법을 제안하였다. 여기서는 영상으로부터 구조적 특징을 효과적으로 추출하기 위하여 PCA를 이용한 방법을 제안한다. 이는 선형투영 및 차원의 감소에 따른 계산부하의 감소로 인식시간을 줄이기 위함이다. 제안된 기법을 10종류의 240*215 픽셀 동물표현의 수화(160개 : 1명*10종류*16동작)영상을 대상으로 City-block의 분류척도를 이용하여 실험한 결과 우수한 인식성능이 있음을 확인하였다.

• Cement
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• s.14
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• pp.74-83
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• 1966

• Cement
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• s.106
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• pp.62-68
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• 1987

• Journal of the Korea Concrete Institute
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• v.20 no.1
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• pp.109-116
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• 2008

This study was performed to get information of self-healing mechanism in cement system and the influence of waterproofing admixtures for concrete on self-healing property. For testing, cement paste specimens cured for 7, 14 and 28 days were prepared and crushed into plate-shape pieces. Screened specimens with thickness not more than 1mm were covered with wet rags and cured in a plastic container for 7 and 28 days. After stopping hydration process of the specimens by treatment with acetone, the surfaces of specimens have been contacted with wet rags were analyzed by XRD, DSC, SEM and EDX. The analysis results showed that cement paste has self-healing property and this property is mainly affected by water. Self-healing in cement system is more effective and faster at an early stage of hydration as there is enough content of unreacted cement to make an additional hydration in this period. The results of this study also showed that waterproofing admixtures for concrete have a considerable effect on self-healing of cement pastes; i.e., they improved self-healing effect of cement and, especially, the specimen using admixture C has shown a lot of needle-like or fibrous hydration products which are estimated as ettringite. It is supposed that these ettringite products are effective to enhance self-healing in cement system.

• Journal of the Korea Concrete Institute
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• v.20 no.5
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• pp.661-668
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• 2008

It is necessary to develop a new technology for effectively reducing hydration heat and controlling thermal cracking caused increasing construction of large size massive concrete structures such as mat foundation of high-rise building, grandiose bridge, and LNG tank. Therefor, to develop a new technology for reducing hydration heat of large size massive concrete in this study, after developing the latent heat binder for controling hydration heat of concrete by application of latent heat material, it was investigated basic properties and durability such as slump, air content and compressive strength, shrinkage properties, permeability, freezing and thawing resistance, corrosion, and hydration heat generation properties of concrete using latent heat binder. As a test result, it was confirmed that latent heat binder was not affected adversely the basic property and durability of concrete, and was advanced on the reduction of hydration heat and control of thermal crack. It is expected to be applied as the excellent technology on the management of hydration heat and thermal crack in large size mass concrete structures.

• Journal of the Korea Concrete Institute
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• v.26 no.3
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• pp.287-297
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• 2014

Heat of hydration of mass concrete is one of the most important factors that significantly affect structural quality and construction period. Therefore, appropriate methods to control heat of hydration are essential technologies for mass concrete construction. In this study, probability of thermal cracking was checked by thermal analysis prior to the construction of a turbine foundation in a domestic power plant. Subsequently, changes of concrete mix proportion and an effective curing method were proposed to control heat of hydration of mass concrete structures. Concrete manufactured by slag cement was proposed instead of concrete produced by ordinary Portland cement, and an automated curing method was proposed to improve the curing method using typical moist curing with blanket. The automated curing method maintains the temperature difference between center and surface of concrete below a setting value by temperature monitoring. Concrete with slag cement was used for actual construction. One of two identical turbine foundations was cured by an insulated curing method, and the other was cured by the automated curing method to compare the curing methods. And then, the effects of control of heat of hydration were evaluated based on temperature/strain monitoring and crack investigations.

• Journal of the Korea Concrete Institute
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• v.28 no.3
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• pp.317-328
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• 2016

This research intends to understand the impact of super-absorbent polymer (SAP) as an internal curing agent in Ultra-High Performance Concrete (UHPC). Two different types of SAPs of acrylic acid (SAP_AA) and acrylic acid-co-acrylamide (SAP_AM) were examined with UHPC formulation. Isothermal calorimetry and x-ray diffraction experiments revealed the impact of polymers with the different chemical bonds on cement hydration. To test its feasibility as a shrinkage reducing admixture for UHPC, a series of experiments including flowability, compressive strength, rapid chloride permeability and autogenous shrinkage profile was performed. While both SAPs showed a reduction in autogenous shrinkage, it has been concluded that the SAP size and chemical form significantly affect the performance as an internal curing agent in UHPC by controlling cement hydration and porosity modification. Between the tested SAPs, SAP_AM which absorbs more water in UHPC than SAP_AA, shows better mechanical and durability performance.

• Journal of the Korea Concrete Institute
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• v.18 no.4 s.94
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• pp.569-576
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• 2006

PC-type copolymers were synthesized using MPEG(polyethylene glycol methyl ether methacrylate, Mn=2080) to different mole ratios of mono-carboxylic acid(AA : acylic acid). The mole ratios of AA were 2, 3, 4 and PC-type terpolymers were synthesized using mono-, dicarboxylic acid(ITA : itaconic acid MAL : maleic acid) with the same graft chain. To investigate effects of PC-type co-, ter-polymers on the hydration of cement experiments involving FT-IR, XRD, DSC, SEM have been analysed with cement paste specimens to 1, 3, 28 day. The hydration reaction rate of cement paste was slightly delayed at 1 day, due to increase in molar ratio of [AA]/[MPEG], it was recovered in the days after and the copolymer was more active than the terpolymer, because of low carboxylic acid content PC-type copolymers applied 2AA-type were fastest copolymer on hydration reaction of cement paste to 3 day and the more AA mole ratios increased, the more hydration was retarded.

• The Korean Journal of Pesticide Science
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• v.9 no.1
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• pp.81-87
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• 2005

Ethaboxam[(RS)-N-(a-cyano-2-thenyl)-4-ethyl-2-(ethylamino)-1,3-thiazole-5-carboximide] is a novel fungicide with high level of activity against Oomycetes fungi. The control effects of ethaboxam technical and various ethaboxam formulations were investigated against P. brassicae, the causal agent of clubroot disease in Chinese cabbage. When ethaboxam was applied to infested soil, club formation caused by P. brassicae was strongly inhibited at 8.33 mg/L soil and $EC_{50}$ of ethaboxam was 2.65 mg/L soil. Five ethaboxam formulations [10% suspension concentrate (SC), 15% SC, 2% granule (GR), 5% GR, 25% wettable powder] and mixture formulation of ethaboxam and metalaxyl (3%+1% GR) exhibited good efficacy against the pathogen. 10% SC, 15% SC, and 2% GR formulations of ethaboxam showed better disease controlling efficacy on Chinese cabbage clubroot than the other formulations. The $EC_{50}$ values of 10% SC, 15% SC, and 2% GR formulations of ethaboxam were 3.72 mg AI/L soil, 1.1 mg AI/L soil, and 4.95 mg AI/L soil, respectively. Among them, soil drenching application by 15% SC formulation of ethaboxam exhibited the most in vivo antifungal activity on P. brassicae. These results indicate that ethaboxam has a high potential for the control of clubroot disease.