• 한국안전학회지
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• 제23권4호
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• pp.59-66
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• 2008

Recently, the deterioration of reinforced concrete structures, primarily due to corrosion of steel reinforcement, has become a major concern. Chloride-induced deterioration is the most important deterioration phenomenon in reinforced concrete structures in harsh environments. For the realistic prediction of chloride penetration into concrete, a mathematical model was developed in which the effects of diffusion, chloride binding and convection due to water movement can be taken into account. The aim of this research was to reach a better understanding on the physical mechanisms underlying the deterioration process of reinforced concrete associated with chloride-induced corrosion and to propose a reliable method for estimating these effects. Chloride concentrations coming from de-icing salts are significantly influenced by the exposure conditions such as salt usage, ambient temperature and repeated wet-dry cycles.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계학술발표회 논문집(I)
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• pp.274-277
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• 2006

There are many structures attacked by chloride ions near a marine environment. And they are attacked by a salt of de-icing chemicals. So, the embedded reinforcement is corroded. In the same time, these are under a fatigue loading by a traffic loading in bridges. In previous studies, there are many researches that deal with a bond behavior under a monotonic loading according to the rate of a steel corrosion. But there are most cases that the steel corrosion and the repeated loading are acted on structures simultaneously. So, in this study, it is investigated a fatigue-bond behavior of RC structures under a steel corrosion and a fatigue loading. Main variables of the test are a corrosion of steel reinforcement and a level of stress.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 가을 학술발표회 논문집(II)
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• pp.1255-1260
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• 2000

The service life is defined as the period of the period of time, until repair becomes necessary to maintain the serviceability of structures. It is getting more common to specify the service life of a structure, particularly structures exposed to de-icing salt water. To accomplish this study, pier in the harbor was chosen as a experimental area. The service life of decks in marine environment was calculated as sum of three period ; initiation period, propagation period and cracking period. The object of this study is to indicate where and how measures can be adopted for checking relevant service lifes.

• Corrosion Science and Technology
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• 제15권1호
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• pp.28-37
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• 2016

Due to the increased construction of offshore concrete structures and the use of de-icing salts for the purpose of snow removal, the needs for the development of anti-corrosive concrete are increasing. To solve these problems, an evaluation of the mechanical and durability properties for concrete were conducted by mixing modified-sulfur as 0 %, 5 %, 10 %, 15 % cement weight ratio. Both strengths and the properties affecting durability such as water absorption coefficient, chloride ion permeability, accelerated carbonation resistance, rapid freezing and thawing, and chemical resistance were evaluated. All evaluations performed were according to the test specifications associated KS. The results indicate that mixing of modified-sulfur lowed chloride ion permeability and improved chemical resistance.

• Advances in concrete construction
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• 제5권6호
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• pp.671-683
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• 2017

Commonly used concrete in general, consists of cement, fine aggregate, coarse aggregate and water. Natural river sand is the most commonly used material as fine aggregate in concrete. One of the important requirements of concrete is that it should be durable under certain conditions of exposure. The durability of concrete is defined as its ability to resist weathering action, chemical attack or any other process of deterioration. Durable concrete will retain its original form, quality and serviceability when exposed to its environment. Deterioration can occur in various forms such as alkali aggregate expansion, freeze-thaw expansion, salt scaling by de-icing salts, shrinkage, attack on the reinforcement due to carbonation, sulphate attack on exposure to ground water, sea water attack and corrosion caused by salts. Addition of admixtures may control these effects. In this paper, an attempt has been made to replace part of fine aggregate by tailing material and part of cement by fly ash to improve the durability of concrete. The various durability tests performed were chemical attack tests such as sulphate attack, chloride attack and acid attack test and water absorption test. The concrete blend with 35% Tailing Material (TM) in place of river sand and 20% Fly Ash (FA) in place of OPC, has exhibited higher durability characteristics.

• 한국구조물진단유지관리공학회 논문집
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• 제14권2호
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• pp.171-175
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• 2010

본 연구는 동결융해, 염해 및 중성화가 복합적으로 작용하는 콘크리트 구조물의 내구성능을 평가하기 위하여 일반강도 콘크리트를 대상으로 동결수를 달리하여 동결융해 시험을 실시함으로서 염해와 동결융해 복합작용에 의한 콘크리트의 열화를 평가하였고, 염해, 동결융해 및 중성화의 세가지 열화가 복합적으로 발생되는 복합열화에 대해서는 적절한 평가방법이 부재하여 동결수에 따른 동결융해 시험 후의 시험체에 대하여 중성화 촉진시험을 실시함으로서 복합열화에 의한 콘크리트 내구성능 저하 특성을 평가하고자 하였다. 본 연구를 통하여 동결수의 종류나 물-결합재비 수준과 무관하게 고로슬래그미분말을 사용한 배합의 경우 염해와 동결융해가 동시에 복합적으로 발생되는 환경에서도 우수한 저항성능을 보이는 결과를 나타내므로 동결융해를 포함한 복합열화 환경에서 충분한 내구성 확보를 위해서는 최소한의 설계기준강도의 확보와 고로슬래그미분말 등 적절한 시멘트 결합재의 선정이 무엇보다 중요하다는 결론을 얻었다.

• 한국조경학회지
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• 제41권4호
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• pp.17-23
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• 2013

본 연구는 가로변 지피식물을 중심으로 염화칼슘에 대한 내성과 피해양상을 파악하여 효율적인 가로변 지피식물 적용 및 관리 자료를 제시하고자 실시되었다. 실험구 조성은 염화칼슘 비율 대조구, 0.5%, 1.0%, 3.0%로 구분하여 일반상토 500g을 기준으로 고상처리 하였다. 식물재료로는 가로수 지피식물로 가능성이 있거나 사용되는 수호초, 옥잠화, 마삭줄, 순비기나무, 사철나무, 작살나무를 사용하였다. 결과를 정리하면 토양은 염화칼슘 농도처리에 따라 산도가 증가하였으며, 전기전도도는 지속적으로 감소하였고, 치환성 칼슘 함량은 처리 이후 증가하였으나 실험기간 중 감소하였다. 수호초, 마삭줄, 사철나무는 염화칼슘 비율 0.5%까지 생육 및 생존이 양호한 것으로 나타났다. 옥잠화, 순비기나무는 1.0%까지 생존이 가능한 것으로 나타났으며, 옥잠화는 식재 기반의 수분을 통한 염류의 이동이 가능한 조건에서 가로변의 지피식재로 적용이 가능할 것이라 판단되었다. 작살나무는 대조구를 제외한 염화칼슘 처리구에서 생육이 불량하고 개엽하지 않아 염화칼슘에 대한 민감성이 큰 것으로 나타났다.

• International Journal of Concrete Structures and Materials
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• 제11권2호
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• pp.199-213
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• 2017

Chloride penetration is among the main causes of corrosion initiation in reinforced concrete (RC) structures producing premature degradations. Weather and exposure conditions directly affect chloride ingress mechanisms and therefore the operational service life and safety of RC structures. Consequently, comprehensive chloride ingress models are useful tools to estimate corrosion initiation risks and minimize maintenance costs for RC structures placed under chloride-contaminated environments. This paper first presents a coupled thermo-hydro-chemical model for predicting chloride penetration into concrete that accounts for realistic weather conditions. This complete numerical model takes into account multiple factors affecting chloride ingress such as diffusion, convection, chloride binding, ionic interaction, and concrete aging. Since the complete model could be computationally expensive for long-term assessment, this study also proposes model simplifications in order to reduce the computational cost. Long-term chloride assessments of complete and reduced models are compared for three locations in France (Brest, Strasbourg and Nice) characterized by different weather and exposure conditions (tidal zone, de-icing salts and salt spray). The comparative study indicates that the reduced model is computationally efficient and accurate for long-term chloride ingress modeling in comparison to the complete one. Given that long-term assessment requires larger climate databases, this research also studies how climate models may affect chloride ingress assessment. The results indicate that the selection of climate models as well as the considered training periods introduce significant errors for mid- and long- term chloride ingress assessment.

• Structural Engineering and Mechanics
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• 제84권3호
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• pp.393-411
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• 2022

A high-performance reactive powder concrete (RPC) has been readied alongside river sand, with 1.25 mm particle size when under the condition of 80C steam curing. As a heat and sound insulation, expanded perlite aggregate (EPA) provides economic advantages in building. Concrete containing EPA is examined in terms of cement types (CEM II 32.5R and CEM I 42.5R), doses (0, 2%, 4% and 6%) as well as replacement rates in this research study. The compressive and density of concrete were used in the testing. At the end of the 28-day period, destructive and nondestructive tests were performed on cube specimens of 150 mm150 mm150 mm. The concrete density is not decreased with the addition of more perlite (from 45 to 60 percent), since the enlarged perlite has a very low barrier to crushing. To get a homogenous and fluid concrete mix, longer mixing times for all the mix components are necessary due to the higher amount of perlite. As a result, it is not suggested to use greater volumes of this aggregate in RPC. In the presence of de-icing salt, the lightweight RPC exhibits excellent freeze-thaw resistance (mass is less than 0.2 kg/m²). The addition of perlite strengthens the aggregate-matrix contact, but there is no apparent ITZ. An increased compressive strength was seen in concretes containing expanded perlite powder and steel fibers with good performance.

• 한국결정성장학회지
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• 제25권5호
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• pp.205-211
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• 2015

황의 대부분은 천연가스와 원유를 탈황시켜 얻게 되며, 국내 정유 플랜트에서는 120만톤 이상 발생하고 있으며, 50 % 정도만이 비료 및 황산등을 만드는 원료로 소모되고 있다. 이에 산업부산물로 얻어지는 황을 콘크리트에 적용하기 위해 개질유황이 제조되고 있어, 이를 활용한 콘크리트의 강도 및 내구성을 평가하였다. OPC에 비해 개질유황 폴리머를 사용할 경우 압축 및 휨강도는 동일 배합수 온도에서는 유사하였으며, 배합수 온도가 증가함에 따라 강도는 다소 증가하였다. 또한 동결융해에 따른 저항성은 개질유황 폴리머의 영향보다는 공기연행제의 사용으로 제어가 됨을 확인하였다. 그리고 5 % 황산 침지에 따른 압축강도 저하율은 개질유황 폴리머를 사용한 콘크리트가 OPC보다 4배 이상 우수하였다. 그리고 제빙염에 대한 표면박리 저항성도 개질유황을 사용한 경우는 표면박리가 발생되지 않은 1등급, OPC의 경우는 골재가 노출되어 4등급으로 평가되었다. 따라서 개질유황 폴리머를 콘크리트에 개질제로 사용할 경우 내구특성이 우수하여 교면포장 등에 효율적으로 사용될 수 있을 것으로 판단된다.