• 대한토목학회논문집
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• 제29권1D호
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• pp.73-80
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• 2009

열화된 콘크리트 구조물 보수에 있어, 보수재를 사용하기 전에 열화부위는 완전히 제거되어야 한다. 워터제트 공법은 열화된 콘크리트를 제거하는 방법 중에 하나로 철근 및 건전한 콘크리트에 손상을 주지 않으면서 손상된 콘크리트를 제거할 수 있는 매우 효과적인 방법으로 알려져 있다. 이러한 워터제트의 사용은 표면요철형성 등으로 신구 콘크리트의 부착력을 향상 시킨다. 본 연구에서는 국내에서 적용되고 있는 워터제트 장비를 사용하여 콘크리트 슬래브 강도에 변화를 주어 파쇄깊이에 따른 강도추정식을 제안하고 하였으며 이를 통해 워터제트 관련 규정제안 및 보수보강 시 사용되고 워터제트 장비에 대한 기초적인 정보를 제공하고자 한다.

• 한국도로학회논문집
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• 제13권2호
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• pp.85-93
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• 2011

본 연구에서는 고로슬래그 미분말 및 플라이애시와 같은 광물질 혼화재를 사용한 친환경 고성능 3성분계 시멘트 콘크리트 교면 포장의 성능을 평가하기 위하여 실험을 하였다. 광물질 혼화재의 혼입률 변화에 따른 3성분계 시멘트 콘크리트의 최적배합을 찾기 위하여 압축강도 및 휨강도 시험을 하였으며 최적배합을 사용하여 내구성 시험인 염소이온 침투저항성, 동결융해, 박리 저항성, 균열 저항성 및 알칼리골재반응 시험으로 친환경 고성능 3성분계 시멘트 콘크리트 교면 표장의 내구성 평가 및 신 구 콘크리트의 부착력을 평가하기 위하여 부착강도 시험을 하였다. 시험결과, 시멘트 70%, 고로슬래그 미분말15% 및 플라이애시 15%의 배합 바인더에서 압축강도 및 휨강도가 우수하게 나타났으며 이를 최적배합으로 도출하였다. 실내 및 시험시공에서 최적 배합을 사용한 실험결과는 염소이온 침투 저항성, 동결융해 저항성, 표면박리 저항성, 알칼리골재 반응 억제 및 내마모성이 우수하게 나타났다. 또한, 특수 제작된 Polymer Cement Mortar(Brooming)를 사용한 신 구 콘크리트의 부착력에서도 우수한 성능을 나타냈다.

• 아동학회지
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• 제11권1호
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• pp.29-44
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• 1990

The present study investigated the concept of Buddha in 9- 12- year-old children who were in the concrete operational stage. The concept of Buddha was investigated in the following dimensions:form, competence and role of Buddha, feelings toward Buddha, and prayer to Buddha. Questionaire data were gathered from 143 children attending the Bulkwang Sunday School Statistical analysis was by Chi square. The children perceived Buddha as (1) a statue or a monk living in their mind and in heaven; and (2) unrestricted and superhuman but different from the creator, keeping an eye on them all the time and everywhere. The role of Buddha was perceived as one of giving blessing with good things to those who pray. The children had diverse feelings of awe, thankfulness, fear and anger toward Buddha. Most of the children were confident that Buddha would respond to their prayers but a few showed some doubt. Children in the concrete operational stage were less credulous than those in the pre-operational stage. More than half of the childen reported that they experience the fulfilment of their prayers. The children had deep faith in attaining Buddhahood.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1993년도 봄 학술발표회 논문집
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• pp.176-181
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• 1993

Recent increasing traffic volumes have made many bridges on highway be widened. Depending on the construction method of bridge widening, several undesirable problems have been arisen with the additional stresses resulting from de-staging of new bridge and the difference of the amount of creep and shrinkage between new and existing bridge. The main focus of this paper is given to investigate the variation of the adhesive strength of steel bar and construction joints of new and old concrete slab. The result shows that repeated vibration loadings was caused some bad effects on the construction joints between new and existing bridges.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2001년도 춘계학술발표대회 논문집
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• pp.135-140
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• 2001

A post-tensioned reinforced concrete slab bridge is analyzed by specially orthotropic laminate theory. Symmetrically reinforced slab with tension and compression steel is considered for convenience of analysis. Each longitudinal and transverse steel layer is regarded as a lamina, and material constants of each lamina is calculated by the use of the rule of mixture. This bridge is under uniformly distributed vertical loads, and axial loads and end moments due to post-tensioning. In this paper, finite difference method is used for numerical analysis of this bridge. Theory and analysis method of specially orthotropic laminate plates used in this paper can be used for design of new bridges, and maintenance and repair of old bridges.

• 자원리싸이클링
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• 제10권1호
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• pp.32-41
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• 2001

택 코트 사용조건에 따른 재활용 아스팔트 혼합물의 부착전단 강도를 평가하였다 시공온도에 따른 부착전단강도를 평가하여 보면 신재와 구재에 상관없이 시공온도 $30^{\circ}C$에서의 값이 $10^{\circ}C$에 비하여 약 10~20%증가함을 알 수 있었다. 또한 재생아스팔트 혼합물의 경우 택 코트를 사용하지 않았을 때 부착전단강도가 특히 낮아서 현장에서 종종 발생하는 접착면 종방향 균열의 직접적인 원인이 될 수 있음을 나타내었다. 택 코트의 양생시간에 대한 부착전단강도의 영향은 시공온도의 영향보다 대체로 적었다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계 학술발표회 논문집(II)
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• pp.325-328
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• 2006

Recently, repair mortars have been mainly used for repairing old concrete structures. In this study, a new repair mortar including shotcrete admixture, slag, silica fume, sulphate and calcium carbonate, was developed for repairing shotcrete layer and the fresh properties and mechanical characteristics of the repair mortar was measured, Test results showed that the shortcrete admixture and other additives reduce the final setting time from about 7 hours to within 20 minutes and increase very early strength and stiffness (within 5 hours after cast).

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1995년도 가을 학술발표회 논문집
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• pp.293-298
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• 1995

This study experimentally evaluate the bonding performance of repair and strengthening materials. It is very important problem to justify bonding properties between repair and strengthening materials and old concrete. Many previous research and investigation showed that bonding strength of reinforcing materials determines the strengthening effect and the durability of repair work. Therefore, menifestation of bonding properties and the improvement of bonding performance of repair and strengthening materials are very important. In order to improve the perforamnce of repair work, it needs to investigate the behavior of bonding materials, such as stress distribution along the bonding area and the long term performance of the material. The target repair methods are steel plate addition technique and repair mortar method, and the test parameters studied in this paper include epoxy thickness, bonding surface texture, and bonding area.

• 산업기술연구
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• 제33권A호
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• pp.93-99
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• 2013

Shotcrete has been referred to as gunite, pneumatically applied mortar or concrete, sprayed concrete or mortar. There are sound reasons why sprayed mortar is one of the best portland cement based material for repairing old concrete structures. However, it is difficult to find the research results on the latex-modified mortar nevertheless on the impact of air onto the fresh and hardened properties of latex-modified mortar. So, the main experimental program included strength test, slump test, rapid chloride permeability test, image analysis for air void system, and chemical attacks with the main experimental variables of latex content, fine aggregate content, water-cement ratio, and air foamer content.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 봄 학술발표회 논문집
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• pp.1017-1022
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• 2003

The hydraulic structures such as aqueduct tunnels and the drainage canal of the hydroelectric power plant in Japan are almost old. Therefore, the concrete surface of the aqueduct tunnel has received damage by wear-out and the crack, etc. This study was to develop repair mortar mixed a coal ash coarse powder by using two kinds of high early strength cements. As a result, the repair mortar was obtained by substituting the EF cement (maid in Japan) and the MT cement (maid in South Korea) at a rate of 60:40, and substituting the coal ash 30% and the mixing rate 35% of the artificial aggregate for natural fine aggregate.