• 콘크리트학회논문집
• /
• 제19권6호
• /
• pp.707-715
• /
• 2007

다공질성 특성을 갖는 콘크리트는 충분한 다짐과 양생 조건에서 장수명을 갖으며, 유해 물질의 주요 경로는 공극이다. 그러나 균열이 발생한 콘크리트의 경우, 균열은 염소이온과 같은 유해 물질의 우선적인 침투 경로가 된다. 균열이 염소에 미치는 영향은 균열폭과 균열 깊이의 크기에 의존한다. 본 연구는 미세균열이 콘크리트의 염소이온 침투에 미치는 영향을 다룬 실험적 연구로서, 연구 목적은 균열폭과 균열 깊이 등의 균열 크기 효과가 염소이온에 미치는 영향을 고찰하는 것이다. 균열을 통한 염소이온의 침투를 시각화 하기 위하여, 급속 염소이온 침투 실험인 RCM (rapid chloride migration) 실험을 수행하였다. 균열폭과 균열 깊이는 전자 현미경으로 관찰하였고, 평균적인 균열폭을 산정하기 위하여 균열 개구 변위가 측정되었다. 다양한 균열 크기에 따른 염소이온의 침투 깊이 및 염소이온 확산계수의 변화율로부터 염소이온이 침투되지 않는 균열 깊이 및 이에 대응한 균열폭이 도출되었다.

• 한국방재학회 논문집
• /
• 제10권1호
• /
• pp.15-22
• /
• 2010

자연환경 중 다양한 형태로 존재하는 염화물은 콘크리트 구조물의 철근 부식을 야기하며 이에 따른 심각한 내구성 저하와 함께 구조물의 수명을 감소시킨다. 현재 콘크리트 중의 염화물 침투 특성을 규명하기위한 연구는 해안가 장기 폭로 시험과 전기화학적 촉진 시험에 의한 확산계수 평가 등에 의해 지속적인 발전을 이루어왔으나 콘크리트의 배합, 수화도, 고정화능력, 공극률의 재료적 특성을 고려한 이성적이며 포괄적인 염화물 침투 모델에 관한 연구는 부족한 실정이다. 따라서 본 연구에서는 실내 염화물 침지 실험을 통해 콘크리트의 염화물 고정화 특성을 파악하고 이를 고려한 염화물 침투 모델로서 비정상상태의 염화물 침투 해석과 함께 해양침지환경하의 철근콘크리트 구조물의 내구수명 예측을 시도하였으며 SHRP 기준과 20~40%의 내구수명의 차이를 보였다.

• 한국안전학회지
• /
• 제23권4호
• /
• pp.59-66
• /
• 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.

• Computers and Concrete
• /
• 제3권6호
• /
• pp.401-422
• /
• 2006

A multi-species model based on the Nernst-Planck equation has been developed by using a finite volume method. The model makes it possible to simulate transport due to an electrical field or by diffusion and to predict chloride penetration through water saturated concrete. The model is used in this paper to assess and analyse chloride diffusion coefficients and chloride binding isotherms. The experimental assessment of the effective chloride diffusion coefficient consists in measuring the chloride penetration depth by using a colorimetric method. The effective diffusion coefficient determined numerically allows to correctly reproduce the chloride penetration depth measured experimentally. Then, a new approach for the determination of chloride binding, based on non-steady state diffusion tests, is proposed. The binding isotherm is identified by a numerical inverse method from a single experimental total chloride concentration profile obtained at a given exposure time and from Freundlich's formula. In order to determine the initial pore solution composition (required as initial conditions for the model), the method of Taylor that describes the release of alkalis from cement and alkali sorption by the hydration products is used here. Finally, with these input data, prediction of total and water-soluble chloride concentration profiles has been performed. The method is validated by comparing the results of numerical simulations to experimental results obtained on various types of concretes and under different exposure conditions.

• 한국도로학회논문집
• /
• 제15권5호
• /
• pp.75-79
• /
• 2013

PURPOSES : The objective of this study is to evaluate the environmental resistance of bio-polymer concrete for use of pavement materials developed for reducing the carbon-dioxide. METHODS : The compression, tension, and bending strength tests were conducted on the bio-polymer concrete specimens with and without environmental conditioning. The specimens were conditioned using the freezing-thaw and accelerated weathering process for long period of time. To assess the resistance against chloride, the chloride ion penetration resistance tests were carried out on the bio-polymer concrete specimens. RESULTS : Test results show that the maximum difference in strength between specimens with and without conditioning is about 2.6MPa indicating that the effect of environmental conditioning on specimen strength is negligible. Based on the chloride ion penetration resistance test, the penetration quantity of electric charge of the specimens is zero and there is no ion penetration within the bio-polymer concrete. CONCLUSIONS : It is found from this study that there is slight change in strength of bio-polymer concretes before and after environmental conditioning process and no chloride ion penetration observed in these specimens. Therefore, the developed bio-polymer concretes can be applied effectively as pavement materials due to the small change of physical properties with environment change.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2001년도 가을 학술발표회 논문집
• /
• pp.503-508
• /
• 2001

With difference to strengthening which could be evaluated structural efficiency, it is hard to do quantitative repair efficiency evaluation achieved compressive strength test or appearance investigation. In this paper, chloride ion penetration test is exacted to core specimens picked from repaired structure for quantitative repair evaluation. The result of experimentation shows repair efficiency quantitatively by means of difference between penetration amount of chloride ion for repaired and unrepaired core specimens.

• 한국건축시공학회:학술대회논문집
• /
• 한국건축시공학회 2015년도 추계 학술논문 발표대회
• /
• pp.111-112
• /
• 2015

There is high possibility of steel corrosion on the reinforced concrete exposed to marine environment by chloride ion penetration. And it show a big difference of concrete durability under conditions of splash zone, tidal zone, and immersion zone. Therefore, in this paper, half-cell potential and chloride ion penetration depth was measured to evaluate the durability of slag concrete by marine exposure experiment. As a result, SC70 specimen showed no steel corrosion, regardless of the marine exposed conditions. Also, a deterrent effect on chloride ion penetration by replacement of slag in tidal zone and immersion zone could be confirmed.

• Corrosion Science and Technology
• /
• 제11권5호
• /
• pp.157-164
• /
• 2012

In first experiment series, this paper is devoted for examining progress of reinforcement corrosion due to carbonation in concrete and to quantify uncarbonation depth to protect reinforcement from corroding. The tolerance of cover depth should be considered in order to prevent carbonation-induced corrosion. From the relationship between the weight loss of reinforcement and corrosion current density for a given time, therefore, the tolerance of cover depth to prevent carbonation-induced corrosion is computed. It is observed that corrosion occurs when the distance between carbonation front and reinforcement surface (uncarbonated depth) is smaller than 5 mm.As a secondary purpose of this study, it is investigated to examine the interaction between carbonation and chloride penetration and their effects on concrete. This was examined experimentally under various boundary conditions. For concrete under the double condition, the risk of deterioration due to carbonation was not severe. However, it was found that the carbonation of concrete could significantly accelerate chloride penetration. As a result, chloride penetration in combination with carbonation is a serious cause of deterioration of concrete.

• 한국건축시공학회지
• /
• 제11권4호
• /
• pp.379-386
• /
• 2011

Durability of concrete is an important issue, and one of the most critical aspects affecting durability is chloride diffusivity. Factors such as water.cement ratio, degree of hydration, volume of the aggregates and their particle size distribution have a significant effect on chloride diffusivity in concrete. The use of polypropylene fibers(particularly very fine and well dispersed micro fibers) or mineral additives has been shown to cause a reduction in concrete's permeability. The main objective of this study is to evaluate the manner in which the inclusion of fiber(in terms of volume and size) and blast furnace slag(BFS) (in terms of volume replacement of cement) influence the chloride diffusivity in concrete by applying 3D computer modeling for the composite structure and performing a simulation of the chloride penetration. The modeled parameters, i.e. chloride diffusivity in concrete, are compared to the experimental data obtained in a parallel chloride migration test experiment with the same concrete mixtures. A good agreement of the same order is found between multi.scale microstructure model, and through this chloride diffusivity in concrete was predicted with results similar to those experimentally measured.

• Advances in concrete construction
• /
• 제2권2호
• /
• pp.109-123
• /
• 2014

This paper presents chloride induced corrosion durability of reinforcing steel in geopolymer concretes containing different contents of sodium silicate ($Na_2SiO_3$) and molarities of NaOH solutions. Seven series of mixes are considered in this study. The first series is ordinary Portland cement (OPC) concrete and is considered as the control mix. The rest six series are geopolymer concretes containing 14 and 16 molar NaOH and $Na_2SiO_3$ to NaOH ratios of 2.5, 3.0 and 3.5. In each series three lollypop specimens of 100 mm in diameter and 200 mm in length, each having one 12 mm diameter steel bar are considered for chloride induced corrosion study. The specimens are subjected to cyclic wetting and drying regime for two months. In wet cycle the specimens are immersed in water containing 3.5% (by wt.) NaCl salt for 4 days, while in dry cycle the specimens are placed in open air for three days. The corrosion activity is monitored by measuring the copper/copper sulphate ($Cu/CuSO_4$) half-cell potential according to ASTM C-876. The chloride penetration depth and sorptivity of all seven concretes are also measured. Results show that the geopolymer concretes exhibited better corrosion resistance than OPC concrete. The higher the amount of $Na_2SiO_3$ and higher the concentration of NaOH solutions the better the corrosion resistance of geopolymer concrete is. Similar behaviour is also observed in sorptivity and chloride penetration depth measurements. Generally, the geopolymer concretes exhibited lower sorptivity and chloride penetration depth than that of OPC concrete. Correlation between the sorptivity and the chloride penetration of geopolymer concretes is established. Correlations are also established between 28 days compressive strength and sorptivity and between 28 days compressive strength and chloride penetration of geopolymer concretes.