• 한국건축시공학회:학술대회논문집
• /
• 한국건축시공학회 2006년도 추계 학술논문 발표대회 논문집
• /
• pp.87-90
• /
• 2006

This study investigates the temperature history of slab mock-up specimens for hot weather concreting applying various surface insulating methods, in order to improve concrete quality at hot weather condition. Test showed that the use of insulating blanket or a bubble sheet on upper section of slab prevented from abrupt increase of temperature and vaporization of moisture during early curing at hot weather circumstance. In addition, it secured higher strength at early age. Therefore it is concluded that concrete construction insulating with the bubble sheet will reduce the plastic and drying shrinkage as well as improve strength at early age, thus securing concrete duality.

• 한국건축시공학회:학술대회논문집
• /
• 한국건축시공학회 2009년도 추계 학술논문 발표대회
• /
• pp.117-120
• /
• 2009

It has been gradually increased with the use of resin based membrane forming agent for curing method, which plays a role in protecting moisture evaporation by forming resin membrane at the surface of concrete. In this paper, tests were carried out to examine moisture retention capability of cement mortar applying membrane forming agent. Dosages and types of the membrane forming agent were varied. It is found that sheet curing sealed with the surface of concrete closely has favorable moisture retention capability. However, the application of membrane forming curing method had superiority in moisture retention capability at early stage but at later age, its capability is deteriorated. Hence, further study regarding altering application method was necessary to secure enhanced moisture retention capability.

• 한국건축시공학회:학술대회논문집
• /
• 한국건축시공학회 2022년도 가을 학술논문 발표대회
• /
• pp.39-40
• /
• 2022

This study is intended to examine the curing effect of the combination of the bubble sheet on the concrete by analyzing the temperature profile and core strength of the simulated concrete structure. The test results relvealed that the average temperature of the concrete applying photothermal sheet overlapped with the double bubble sheet at the bottom was 23.5℃, which had the highest insulation and insulation effect compared to other types of surface insulation curing sheets, and the core strength increased by up to 56%.

• Computers and Concrete
• /
• 제34권2호
• /
• pp.231-245
• /
• 2024

A 3D discrete element model integrating the rough surface contact concept with the flat-joint model is suggested to examine the mechanical characteristics of the interfacial transition zone (ITZ) in concrete. The essential components of our DEM procedure include the calculation of the actual contact area in an element contact-pair related to the bonded factor using a Gaussian probability distribution of asperity height, as well as the determination of the contact probability-relative displacement form using the least square method for further computing the force-displacement of ITZs. The present formulations are implemented in MUSEN, an open source development environment for discrete element analysis that is optimized for high performance computation. The model's meso-parameters are calibrated by using uniaxial compression and splitting tensile simulations, as well as laboratory tests of concrete from the literature. The present model's DEM predictions accord well with laboratory experimental tests of pull-out concrete specimens published in the literature.

• 콘크리트학회논문집
• /
• 제26권1호
• /
• pp.79-86
• /
• 2014

이 연구는 표면매입 보강된 FRP 판과 콘크리트사이의 응력전달기구를 이론적으로 연구한 것으로서 이선형 부착모델을 이용하여 부착거동을 묘사하고 이를 실험 결과와 비교하여 신뢰성있는 해석방법을 제시하였다. 연구로부터, 표면매입된 FRP 판과 콘크리트사이의 계면특성을 고려한 미분방정식에 이선형 부착-미끄러짐 관계곡선을 사용하여 해석할 경우, 모델의 임계값인 최대전단강도와 미끄러짐 변위, 그리고 박락에 의한 연화거동이 시작될 때의 변위값 선정과정이 제시되었다. 또한 제안된 모델을 사용하여 부착길이가 다르게 보강된 표면매입 FRP 판의 미끄러짐 거동을 해석한 결과 실제 거동을 매우 근사하게 묘사할 수 있는 것으로 나타났다.

• 한국건축시공학회:학술대회논문집
• /
• 한국건축시공학회 2011년도 추계 학술논문 발표대회
• /
• pp.199-200
• /
• 2011

Absorption of lightweight aggregate affects the properties of fresh and hardened concrete, so care must be taken. In this study, according to KS F 2533 absorption is measured to aggregate size, submerged time, holding time and practically ways to maintain a constant absorption was to seek. The findings for quality control of the lightweight aggregate concrete mixture is saturation of the surface-dry aggregate humidity 100% after 24 hours immersion in the environment has been stored for more than two days to absorb the state was able to define. Dry density at the surface of the lightweight aggregate and lightweight concrete mix design and placement is possible for it to apply.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2004년도 추계 학술발표회 제16권2호
• /
• pp.813-816
• /
• 2004

This study was performed to investigate bonding performance of epoxy resins for repairing of cracks in concrete, as a part of project to establish quality control standard for epoxy resins. In the slant shear strength test for hard and soft type epoxy, hard type was higher about 3 times than soft one. From the results, it is thought that hard type is suitable for load carrying. Injection of epoxy resin in the notch made flexural strength increase about $47\%$ over the specimen that epoxy resin is not injected. There were no differences in bonding performances with viscosity. Application of epoxy resin on the wet concrete surface made slant shear strength decrease about $46\%$, but similar performance to the case of application on the dry surface appeared by using epoxy resin for wet condition.

• 한국전산구조공학회:학술대회논문집
• /
• 한국전산구조공학회 2004년도 가을 학술발표회 논문집
• /
• pp.312-319
• /
• 2004

This paper is mai y focused to develop new concrete material model such as ultimate failure surface in compression-compression region, hardening rule and cracking criteria which are basically used in the nonlinear finite element analysis of nuclear prestressed concrete containment building. From the Kepri's experimental results, failure surface of the concrete based on the elasto-plastic material model is modified and new cracking criteria is proposed. Nonlinear FE analysis program using a new material model is implemented to analysis plane concrete. Finally, numerical simulation to compare the performance of the new material model with experimental results is employed. The numerical results by the proposed model in this study agree very well with the experimental data.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2005년도 추계 학술발표회 제17권2호
• /
• pp.475-478
• /
• 2005

Deicing salt has been generally used for traffic safety in winter, and the amount is increasing every year. However, deicing salt may induce the decrease of bond strength, surface scaling, and environmental pollution, etc. the purpose of this paper is to suggest the fundamental data on safety and durability for concrete structures through the estimation of chloride concentration profile and chloride diffusion coefficient. According to the test results, the critical chloride concentration($0.9\~1.2kg/m^3$)was measured at depth $23\~30mm$, and the limit chloride concentration($0.3kg/m^3$)was reached to depth 40mm. Also the surface chloride amount indicates 3.45kg per concrete unit weight, and the results showed the possibility of corrosion by deicing salt penetration.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 1992년도 봄 학술발표회 논문집
• /
• pp.74-79
• /
• 1992

The confinement of concrete from splitting bond failure is studied with the experiments and finite element models. The cracks in the test beam-end specimens containing various covers show a typical splitting failure with a dominant fracture surface. The finite element model includes representation of the splitting cracking using Hillerborg's fictitious crack model. The increase in bond strength from addition of covers are consistant for both test bars and numerical models. The numerical solution agrees well with results and also with the test results and also with the empirical equations. The splitting crack in the numerical models generally matches the crack surface observed in the laboratory. The confinement of concrete from splitting is one of the governing factors in the ultimate bond force.