• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.401-404
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• 2008

Crack is a penetration path of harmful material such as chloride ion, and causes a serious deterioration in durability. So, the characteristics of chloride penetration are investigated for the cracked flexural concrete members using high-durable materials. For these, the flexural crack of beam specimen is introduced by transverse loading. And, Rapid Chloride Penetration Test (RCPT) and Long-term chloride penetration test are carried out to compare the chloride penetration depth. From test results when crack is happened, the chloride penetration resistance of the durable member was superior than that of the normal member. Blast furnace slag concrete member has a excellent chloride penetration resistance in long-term chloride penetration test.

• Journal of the Korea Concrete Institute
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• v.14 no.1
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• pp.100-109
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• 2002

Significant damage to concrete results from the intrusion of corrosive solutions, for example, dissolved chlorides corrode reinforcing steel and cause spatting. Effectively blocks the penetration of these solutions will eliminate or greatly reduce this damage and lead to increased durability. This study is to investigate the effects of pozzolanic admixtures, fly ash and silica fume, and a blast furnace slag on the chloride ion penetration of concretes. The main experimental variables wore the water-cementitious material ratios, the types and amount of admixtures, and the curing time. And it is tested for the porosity and pore size distributions of cement paste, chloride ion permeability based on electrical conductance, and 180-day ponding test for chloride intrusion. The results show that the resistance of concrete to the penetration of chloride ions increases as the w/c was decreased, and the increasing of curing time. Also, concrete with pozzolans exhibited higher resistance to chloride ion penetration than the plain concrete. The significant reduction in chloride ion permeability(charge passed) of concrete with pozzolans due to formation of a discontinuous macro-pore system which inhibits flow. It is shown that there is a relationship between chloride ion permeability and depth of chloride ion penetration of concrete, based on the pore structure (porosity and pore size distributions) of cement paste.

• Journal of the Korea Concrete Institute
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• v.15 no.3
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• pp.400-408
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• 2003

Chloride ion inside concrete destroys the so-called passive film surrounding reinforcing bars inside concrete so that the so-called salt attack accelerates corrosion which is the most critical factor for durability as well as structural safety of reinforced concrete structures. Recently, as a solution of the salt attack, the ground granulated blast-furnace slag(GGBFS) have been used as binder or blended cement more extensively. In this paper, characteristics of chloride ion diffusion for the GGBFS concrete, which is known to possess better resistance to damage due to the chloride ion penetration than ordinary portland cement(OPC) concrete possesses, are analyzed and a chloride ion diffusion model for the GGBFS concrete is proposed by modifying an existing diffusion model for the OPC concrete. The proposed model is verified by comparing diffusion analysis results using the model accelerated chloride penetration test results for concrete specimens as well as field test results for an RC bridge pier. Then, an optimal resistance condition to chloride penetration for the GGBFS concrete is obtained according to degrees of fineness and replacement ratios of the GGBFS concrete. The result shows that the GGBFS concrete has better resistance to chloride ion penetration than OPC concrete has and the resistance is more affected by the replacement ratio than the degree of fineness of the GGBFS.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.513-516
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• 2008

In this study the prediction model of Chloride Ion progress rate of concrete using steel powder as an addition is developed, in which the reduction of not only the diffusion rate of $Cl^-$ but also the corrosion rate by replenishment of pore by corrosion products. The model is based on the diffusions of $Cl^-$ and its reaction with $Fe^{2+}$, in chloride attack progression region. The model can also explain the characteristics of chloride ion permeation resistance of concrete that the matrix is densified due to corrosion products. The prediction by the model agreed well the experimental data in which the concrete using steel powder, and it showed the lower rate in long-term age to Chloride Ion progress rate than the concrete without steel powder. Consequently the model can predict Chloride Ion progress rate of concrete exposed in the atmosphere regardless of the water-to-cement raito, the amount of the content of steel powder, etc.

• Journal of the Korea Concrete Institute
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• v.29 no.3
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• pp.299-306
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• 2017

In this research, it was examined chloride ion penetration resistance of slag-replaced concrete and cementless slag concrete considering marine environmental exposure conditions of splash zone, tidal zone and immersion zone. In the design strength of grade 24 MPa, the specimens were tested to determine their compressive strength, scanning electron microscopy images and chloride migration coefficient. Further, chloride ion penetration depth and carbonation depth of specimens exposed to marine environment were measured. Experimental results confirm that chloride migration coefficient of specimens tended to decrease with increasing the replacement ratio of ground granulated blast-furnace slag in accelerated laboratory test. In addition, the specimens exposed to the tidal zone were found to be the greatest chloride ion penetration depth compared to splash zone and immersion zone. On the other hand, the chloride ion penetration depth of the specimens exposed to splash zone tended to increase with increasing the replacement ratio of ground granulated blast-furnace slag in contrast with the results for the tidal zone and immersion zone.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.1
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• pp.78-84
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• 2019

The Marine concrete that located at immersion zone receives an hydrostatic pressure of 1 atm as depth of the water increased by 10 m. And it could accelerate chloride ion penetration. In this study, to evaluate the influence of hydrostatic pressure on chloride ion penetration, concrete mixed by ordinary Portland cement and Portland blast-furnace slag cement was exposed to 1 and 6 atm and substitute ocean water. As a result, the surface chloride ion concentration of the concrete under 6 atm of hydrostatic pressure increased rapidly and the water-soluble chloride ion contents was increased by depth. In addition, the concrete under 6 atm of hydrostatic pressure showed the increase of capillary pores corresponding to 5~100 nm.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.4A
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• pp.365-371
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• 2009

It is time-consuming to estimate chloride diffusivity of concrete by concentration difference test. For the reason chloride diffusivity of concrete is mainly tested by electrically accelerated method, which is accelerating the movement of chloride ion by potential difference. In this study, portland cement concrete and concrete containing with ground granulated blast-furnace slag (40 and 60% of cement by weight) with water-cementitious material ratio 40, 45, 50 and 60% were manufactured. To compare with chloride diffusivity calculated from the electrically accelerated test and immersed test in artifical seawater, chloride diffusivity tests were conducted. From the results of regression analysis, regression equation between accelerated chloride diffusivity and immersed chloride diffusivity was linear function. And the determinant coefficient was 0.96 for linear equation.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.3
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• pp.138-143
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• 2010

Recently, as many big marine concrete structures increase, it is necessary that chloride ion diffusion coefficient of concrete shall be evaluated but it will take a long time to evaluate chloride ion diffusion coefficient of concrete. Accordingly, many test methods are suggested to evaluate chloride ion diffusion coefficient in a short period time by the promotion in electro chemical ways but the systematic study for this is insufficient. Therefore, this study evaluates chloride ion penetration and diffusion features by three representative electric promotion tests targeting for three different cements whose ingredients are different and analyzes the correlationship between them. As a result, diffusion features of chloride ion varied according to the cement ingredients and three ingredients cement in which blast furnace slag powder and fly ash are mixed in constant ratio, which shows the most excellent cement diffusion properties. For diffusion properties of chloride ion, the correlationship between test methods are good.

• Magazine of the Korea Concrete Institute
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• v.9 no.6
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• pp.233-241
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• 1997

최근 해안환경하에 있는 콘크리트구조물의 철근부식은 구조물의 내구성 저하 및 유지관리라는 차원에서 커다란 문제점을 가지고 있다. 이와 같은 현상은 해양구조물의 건설이 날로 증가하고 있고, 또 콘크리트 제조시 잔골재의 일부를 염분이 함유된 해사를 사용함으로써 더욱 심각해지고 있다. 본 연구에서는 콘크리트 표면으로부터 침투해 들어오는 침입염분의 거동을 모델화하였으며, 콘크리트 세공속의 수용액상에 있은 염화물이온의 확산을 포함하는 물리 화학적 진행, 시멘트 수화물에 고정되는 염분의 흡착과 탈착 및 고정염과의 화학반응 등의 현상을 유한요소법에 의해 해석을 실시하였다. 본 연구의 결과는 콘크리트 내부의 철근 발청시기의 예측, 해안환경하에 있는 콘크리트 구조물의 침투 염분에 의한 콘크리트 덮개의 결정, 콘크리트 구조물의 염화물이온의 허용치 설정을 비롯하여 내구년수를 예측하는데 유용하게 활용될 수 있을 것으로 기대된다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.2
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• pp.79-87
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• 2011

In this study, the chloride penetration tests were performed for the initially cracked reinforced concrete members. The chloride diffusion characteristics and the critical crack width are compared, and the properties of self-healing are investigated. According to the test results, the chloride penetration resistance was greatly reduced as the surface crack width increased. When the mineral admixtures are added, the chloride penetration resistance of uncracked specimens were effectively increased, however, in case of the blast furnace slag and fly ash, the cracked specimens showed the more reduced resistance than OPC case, inversely. Also, the critical width was $29{\mu}m$, on average, for immersion test. The crack width with $4{\sim}15{\mu}m$ was restored by self-healing, The parts restored by self-healing were seemed to be visually restored, however, the chloride penetration resistance was not restored, perfectly.