• Magazine of the Korea Concrete Institute
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• v.8 no.3
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• pp.157-165
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• 1996

The purpose of this study is to develop the epoxy-modified mortars and concretes without hardener having a good balance between performance and cost. In this study, the epoxy-modified and concretes without and with the hardener are prepared with various polymer-cement ratios, and tested for the mechanical properties of the epoxy-modified mortars and concretes without and with the hardener. From the test results, the epoxy-modified mortars and concretes without the hardener having an excellent mechanical properties are developed at low polymer-cement ratios of 10 to 20% compared with those of conventional epoxy-modified mortars and concretes with the hardener.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.4A
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• pp.295-302
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• 2011

The setting time which is the important element for the determination of slip-up speed of Slip-Form system is the hardening time of early-age concrete when the in place concrete has minimum compressive strength before the concrete appears out of Slip-Form system. But it is very difficult to predict the setting time because it depends on not only the composition ratio of concrete but also various conditions of construction fields. Thus, the technique to estimate accurately and continuously the hardening time of early-age in place concrete during operating Slip-Form system is necessary to guarantee the safety of Slip-Form system and the maintenance of the shape of concrete. Ultrasonic wave-based nondestructive testing methods have the advantages which are accurate and continuous in estimating concrete compressive strength. Of such methods, the method using surface wave which propagates along the surface of material is effective for thick member such as a pylon. Thus, in this paper a study on the determination of slip-up speed for Slip-Form system using surface wave velocity is performed. The relation between the slip-up speed of Slip-Form system and the setting time is formulated, and the surface wave velocity is estimated from continuous wavelet transform of the numerical results for surface wave propagation. Finally, the accuracy of this method according to the distance between the wave source and receivers and the relation between the estimated surface wave velocity and the elastic modulus are investigated.

• Proceedings of the Korean Institute of Industrial Safety Conference
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• 1999.06a
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• pp.293-296
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• 1999

콘크리트에서 발생되는 균열은 구조물의 내구성뿐만 아니라 구조물의 안전성에도 악영향을 미치게 하며, 경우에 따라서는 사회적인 문제로까지 대두되기도 한다. 콘크리트의 균열은 크게 굳지 않은 콘크리트와 경화콘크리트에서 발생될 수 있는 균열로 나눌 수 있다. 굳지 않은 콘크리트에서 발생될 수 있는 균열요인으로는 대표적으로 콘크리트의 초기동결, 소성침하, 거푸집 및 동바리의 조기제거 등을 들 수 있고, 경화콘크리트에서는 물리ㆍ화학적요인, 열적요인, 구조적요인 등을 들 수 있다. 이러한 여러 가지의 균열요인 중에서 최근들어 열적요인에 해당되는 매스콘크리트의 온도균열 문제가 자주 대두되고 있는 실정이다. (중략)

• 레미콘
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• no.10 s.53
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• pp.16-38
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• 1997

• Journal of the Korean Society for Nondestructive Testing
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• v.36 no.3
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• pp.217-224
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• 2016

This paper presents a new technique for monitoring the concrete curing process using embedded piezoelectric transducers via admittance measurements. When a piezoelectric transducer is embedded in a structure, the electrical impedance (admittance) of the transducer is coupled with the mechanical impedance of the host structure, which allows monitoring of the structural condition. In this study, the admittance signatures are used for monitoring the concrete curing process. This new method is based on an admittance-based sensor diagnostic process, in which the capacitance values of the piezoelectric transducers are dependent on the strength of the host structure. We numerically and experimentally investigated the variations in capacitive value during the curing process. The results demonstrate that there is a clear relationship between the concrete curing status and the slope, this indicates that the proposed method could be efficiently used for monitoring the curing status of a concrete structure.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.3 no.2
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• pp.73-85
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• 1983

We occasionally find a thin layer of imperfectly hardened concrete surface when the wood form is stripped off. It has been generally believed that the principal causes were the effects of reactive form oil, adhesive agent or formalin which has been used in the course of plywood manufacturing. However, in this experiment, it became clear that the concrete surface could be influenced more harmfully by a certain species of wood form and the storage conditions of wood form rather than any other causes. Especially, the main cause of the severely dusty layer is the use of wood form exposed to sun for a long period. Countermeasures, therefore, for preventing concrete surface from dusting are also discussed in this paper.

• 레미콘
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• no.4 s.51
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• pp.60-67
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• 1997

• Proceedings of the Korea Concrete Institute Conference
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• 1993.10a
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• pp.162-166
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• 1993

폴리머 콘크리트에 대한 연구는 세계 각국에서 오래전부터 수행하여 구조물에 적용한다든가 보수재로 사용하고 있는데 비해 국내에서의 연구는 최근에 시작되었으며, 폴리머 콘크리트에 대한 재료의 기초적 특성 연구가 활발히 진행되고 있으나 체계적인 연구 결과나 실용화 실적이 적다. 따라서 본연구에서는 폴리머 콘크리트의 초기경화 특성을 고찰하여 콘크리트 포장의 보수재료로서의 폴리머 콘크리트의 활용 토대를 구축하고자 한다.

• Journal of Korean Association for Spatial Structures
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• v.9 no.4
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• pp.61-72
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• 2009

As a trend of construction has become high-rise and larger, it is necessary to reduce the self-weight of structures and buildings. One of the most effective methods to reduce the self-weight of structures and buildings is to use the lightweight aggregate concrete. To complement the strength of the lightweight aggregate concrete, polymer was added to concrete's mixing. In this study, experiments to make the moderate mixing proportion of polymer modified lightweight concrete were performed. Also the hardened concrete tests were performed to investigate the physical characteristics of the polymer-modified lightweight aggregate concrete. As a result, the flexural strength was increased by a small quantity of SBR Latex. Based on the test results the estimating equation was proposed through the regression analysis.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.445-448
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• 2008

The unsaturated polyester(UP) and epoxy resin have a superior material properties and a chemical resistance using sewerage pipes rehabilitation. However, UP and epoxy have not a low temperatures harding, the requirement $8{\sim}11$ hours long times harding and heating system used by reinforcement liner. This study is to evaluate the effects of low temperature harding properties methyl methacrylate(MMA) monomer using expanded polystyrene(EPS) and UP in addition of initiator and promoters. From the test result, viscosity tends to increase with increasing EPS and UP contents. However, harding time change of the MMA resins which it follows in addition of the initiator and promoter.