• Journal of the Korea Institute of Building Construction
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• v.10 no.6
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• pp.97-107
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• 2010

This study outlines a successful and effective plan for repairing water-leakage cracks in concrete structures. The lack of adequate solutions for water-leakage cracks often results in unnecessarily high repair costs, and as such this remains a problem that requires constant attention. Unfortunately, despite the availability of a vast number of different materials and methods, it is often difficult to attain a perfect waterproof sealing The reason for the difficulties in the repair of water-leakage cracks can be attributed to an insufficient knowledge and understanding of the negative factors (i.e., chemical and physical (mechanical) conditions) that cause water-leakage cracks, and of the properties of the repair materials and methods. In this study, guidelines and methods for the selection of adequate materials for the repair of water-leakage cracks in concrete structures were developed for countries that do not already have general guidelines on this subject, and for local regulatory authorities elsewhere.

• Journal of the Korea institute for structural maintenance and inspection
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• v.2 no.1
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• pp.108-120
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• 1998

많은 주거용 및 상업용 건물에서 콘크리트 구조물이 사용되고 있는데 콘크리트 슬래브 아래의 기초부분에 공동이 생기는 경우가 종종 발견되었다. 이 현상은 진동하중, 반복되는 충격, 흙의 유실, 혹은 불량시공 등 여러가지 이유에 의해 발생할 수 있다. 이러한 현상은 구조물의 지지력을 저하시키고 결국 수명을 단축시키는 원인이 되므로 이러한 문제는 일찍 발견되고 조치가 취해질수록 구조물의 수명을 연장시킬 수 있을 것이다. 이러한 공동이 슬래브 아래에서 형성되고 커져가는 과정을 모니터할 수 있으면 현재 상태에서 지지력을 결정하고 또한 앞으로 남은 수명을 예측함으로써 적절한 유지보수계획을 세우는 데에 큰 도움이 될 것이다. 이 연구에서는 음파와 응력파, 특히 표면파가 슬래브 아래의 공동을 찾아내는데 이용되었고 두 가지 방법의 효과가 상호 비교되었다. 두개의 콘크리트 슬래브를 만들어 이용했는데 하나는 미리 공동이 만들어져 있었고 다른 하나에는 공동이 없었다. 공동이 없던 슬래브는 처음 손상안된 상태에서 실험을 한 후 나중에 하부에 공동을 만들어 다시 실험하였다. 실험결과와 실제 공동의 위치가 잘 일치되는 것으로 나타났다. 응력파를 이용하는 방법과 음파를 이용하는 방법사이의 장단점이 비교검토되었고 실험의 표준방법과 결과에 대한 일반적인 기준이 확립되어야 하는 필요성에 대해서도 설명되었다.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2013.04a
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• pp.29-30
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• 2013

폴리머 시멘트 모르타르(Polymer-Modified Cement Mortar, 이하, PCM으로 칭함)는 일반 시멘트 모르타르와 비교해서 접착성, 치밀성, 내약품성, 시공성등이 우수한 재료로, 콘크리트 구조물의 보수 보강에 필수불가결한 재료로 인식되고 있다. 그러나, 혼입된 폴리머는 유기물 재료로, 화재와 같은 고온을 받는 경우에는 무기계 재료인 일반 모르타르 및 콘크리트와는 또 다른 고온역에서의 성상을 보일 것으로 예상된다. 이로 인해, PCM으로 보수 보강된 건축물에 화재가 발생할 경우, 고온에서의 안전성 및 화재 후의 보수 보강 필요성에 대한 평가를 행할 필요가 있다. 이에 본 논문에서는 평가시 기본적인 데이터로 활용될 수 있는 PCM의 고온노출시의 역학적 특성에 대한 검토방안으로, 기존의 실험조건 및 실험방법을 응용한 새로운 실험방법을 적용, 비교검토를 행하고, 고온영역에서의 PCM의 역학적 특성에 대해 고찰했다.

• Journal of the Society of Disaster Information
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• v.13 no.4
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• pp.562-569
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• 2017

Reinforced concrete is used for bridges and large structures that are constructed with social overhead capital because they are economically and semi-permanently integrated with reinforcing bar and concrete. However, when the chloride ion in the concrete destroys the passive film of the reinforcing bar by the marine exposure environment and the snow remover used in the winter season, and the reinforcing bar is corroded by various chemical and physical actions, the durability is deteriorated in a short period, and the life span is shortened. In this study, a repair method to recover the durability of the initial structure by effectively removing chloride ion from the damage caused by salting of the above mentioned reinforced concrete was conducted.

• Journal of the Korea institute for structural maintenance and inspection
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• v.11 no.6
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• pp.77-86
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• 2007

The repair technique utilizing surface impregnant is widely used due to its simple construction procedures and economical benefit. Surface protection through this reparing technique cannot increase the bearing capacity of concrete members much but increase the durability performance and service life efficiently. In this study, fundamental tests such as water suction and permeation are performed for concrete specimens with several organic/inorgarnic impregnant and suitable impregnant is selected on the basis of the results. Finally, durability tests such as carbonation, freezing and thawing, and chloride attack are carried out for the concrete specimens with selected impregnant and it is experimentally verified that they have good resistance to deteriorations.

• Journal of the Korean Recycled Construction Resources Institute
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• v.2 no.1
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• pp.1-9
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• 2014

In this paper, $CO_2$ amount is evaluated considering repairing timing and unit $CO_2$ amount per repair method including various stage of material manufacturing, moving, and construction. Four mix proportions with mineral admixture are considered and repairing timing/numbers are simulated based on the results from Life 365 which can handle chloride penetration. Furthermore two repair methods (simple cover concrete replacement and replacement with electro-chemical method for removing chloride content) are considered and the related $CO_2$ emissions are evaluated. From the study, the case with high W/B (water to binder ratio) ratio shows smaller $CO_2$ emission in construction stage but it increases more rapidly with increasing number of repair. $CO_2$ emission considering electro-chemical method greatly increases with the increasing unit $CO_2$ for the repairing method. The numbers of jumping step (repairing number) are evaluated to be 9 for WB37-OPC, 18 for WB50-OPC, 4 for WB40-SG, and 7 for WB47-SG respectively. RC structures with the longer maintenance free period are evaluated to be advantageous for saving $CO_2$ emission.

• Journal of the Korea Concrete Institute
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• v.22 no.2
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• pp.149-158
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• 2010

Recently, numerous construction techniques for repairing and strengthening methods for above ground or air exposed concrete structure have been developed. However repairing and strengthening methods for underwater structural members under continuous loading, such as piers and steel piles need the further development. Therefore, this study develops an aqua epoxy, which can be used for repairing and strengthening of structural members located underwater. Moreover, using the epoxy material and strengthening fibers, a fiber reinforced composite sheet called Aqua Advanced FRP (AAF) for underwater usage is developed. To verify and to obtain properties of the material and the performance of AAF, several tests such as pull-off strength test, bond shear strength test, and chemical resistance test, were carried out. The results showed that the developed aqua epoxy does not easily dissolve in wet conditions and does not create any residual particle during hardening. In spite of underwater conditions, it showed the superior workability, because of the high viscosity over 30,000 cps and adhesion capacity over 2 MPa, which are nearly equivalent to those used in dry conditions. In case of the chemical resistance test, the developed aqua epoxy and composite showed the weight change of about 0.5~1.0%, which verifies the superior chemical resistance.

• Magazine of the Korea Concrete Institute
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• v.18 no.1 s.90
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• pp.56-61
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• 2006

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.3
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• pp.153-159
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• 2018

Many researches have been carried out on carbonation, a representative deterioration in underground structure. The carbonation of RC (Reinforced Concrete) structure can cause steel corrosion through pH drop in concrete pore water. However extension of service life in RC structures can be obtained through simple surface protection. Unlike the conventional deterministic maintenance technique, probabilistic technique can consider a variation of service life but it deals with only normal distributions. In the work, life time-probability distributions considering not only normal but also log distributions are induced, and repair cost estimation technique is proposed based on the induced model. The proposed technique can evaluate the repair cost through probabilistic manner regardless of normal or log distribution from initial service life and extended service life with repair. When the extended service life through repair has log distribution, repair cost is effectively reduced. The more reasonable maintenance strategy can be set up though actual determination of life-probability distribution based on long term tests and field investigations.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.5
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• pp.128-135
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• 2010

Polymer-modified cement mortar(PCM) has been widely used for strengthening of the concrete structures due to its excellent physical properties such as high strength and durability. Adhesive strength or behavior, on the other hands, between PCM and concrete is very important in strengthening the concrete member using PCM. Therefore the adhesive failure mechanism between PCM and concrete should be fully verified and understood. This study was performed to evaluate adhesive strength of PCM to the concrete by the direct pull-out test. In the direct pull-out tests, the adhesive strength under the various pre-treatment conditions such as immersion, thunder shower, freezing and thawing are evaluated. Also, the field direct pull-out test are performed to investigate the adhesive strength of mock-up test specimens. In the results of the test, the adhesive strength value by field test are lower than those of the standard curing condition. From these comparison and investigation, field test result was similar with the thunder shower test result. The results of the test was used to evaluate the korean industrial standard of polymer modified cement mortars for maintenance in concrete.