무기질 혼화재가 해양콘크리트의 염화물 고정화에 미치는 영향

김노동(Kim, No-Dong),박상준(Park, Sang-Joon) 대한건축학회 2014 大韓建築學會論文集 : 構造系 Vol.30 No.6

The use of industrial by-products is extending steadily in concrete admixtures. However, the effects of these mineral admixtures on the chloride binding in concrete have been insufficiently studied. In this study, the chloride binding effect of various mineral admixtures is evaluated and the results can be drawn as follows. The resistance to chloride penetration was greatly improved when ground granulated blast-furnace slag (GGBS) and silica fume (SF) was used in concrete. The chloride penetration resistance of concrete used fly ash (FA) was improved after 91 days. The chloride penetration depth of concrete used GGBS was lowest and concrete used SF showed second-lowest penetration depth. Concrete used FA having the effect of long-term strength development by pozzolanic reaction showed the lowest resistance to chloride penetration. In case of concrete used only ordinary portland cement, chloride migration coefficient reduced approximately 40.3% when compressive strength increased 10%. Chloride migration coefficients of concrete used FA, SF and GGBS was reduced 24.9%, 23.0% and 14.1%, respectively. Soluble chloride content was various with types and replacements of mineral admixtures in range of 41% to 77% of total chloride content. The chloride binding effect of concrete used FA was highest because concrete used FA was not denser than concrete used GGBS or SF and chloride ion penetrated inside more. However, concrete used GGBS or SF was dense and chloride ion concentrated inner surface portion of specimen. It caused lower chloride binding effect of concrete used GGBS or SF.

음이온교환수지 분말이 치환된 포틀랜드 시멘트 모르타르의 염소이온 침투 특성

이윤수 ( Lee Yun-su ),임승민 ( Lim Seung-min ),박장현 ( Park Jang-hyun ),정도현 ( Jung Do-hyun ),이한승 ( Lee Han-seung ) 한국건축시공학회 2020 한국건축시공학회지 Vol.20 No.1

외부로부터 시멘트 복합체 내부로 침투되는 염소이온은 주로 농도차로 인한 확산을 통해 이동한다. 확산하는 염소이온 중 일부는 일반적으로 내부 수화물과의 반응을 통해 고정되는데, 최근의 몇몇 연구는 음이온 교환 수지(AER) 분말이 혼입된 시멘트 복합체의 염소이온 침투 저항성 및 고정능력에 관한 연구결과를 보여주었다. 본 연구에서는 AER이 분쇄되는 과정에서 염소이온 흡착능력이 상실하는지를 확인하고자 한다. AER 분말의 염소이온 흡착능력은 증류수와 포화수산화칼슘 수용액 조건에서 분석되었고, AER 비드의 염소이온 흡착능력에 관한 기존의 연구결과와 비교되었다. 추가로, AER 분말이 포틀랜드 시멘트의 일부 치환된 모르타르의 압축강도 측정, 염소이온 확산계수 도출(NT Build 492 시험방법 이용), 염소이온 침투 프로파일링(전자현미분석 이용)을 수행하였다. 본 연구의 실험 결과는 분쇄과정으로 인한 AER 분말의 염소이온 흡착능력 저하가 거의 없음을 보여주었다. 그리고 AER 분말은 모르타르 내에서도 염소이온을 빠르게 흡착할 수 있었고, 시멘트 수화물보다 우수한 염소이온 흡착성능을 보여주었다. Chloride ion, which penetrates into the cement composites from the outside, generally diffuses by the concentration gradient. Chloride ions are adsorbed by the chemical reaction with cement hydrates. Recent studies have shown that anion exchange resin (AER) powder can effectively adsorb the chloride ion in the cement composites, and thus, the cement composites containing AER have a high chloride adsorption capacity and a good resistance for chloride penetration. In this study, the chloride adsorption ability of the AER powder was investigated under the conditions of distilled water and calcium hydroxide saturated solution to determine if the AER powder is less effective to increase the chloride adsorption ability after grinding process. The chloride adsorption ability of AER powder was compared with the previous research about the chloride adsorption of AER bead. In addition, the compressive strength, chloride diffusion coefficient (using NT Build 492 method), and the chloride profile of cement mortar substituted with AER powder were investigated. There was no decrease in the chloride adsorption capacity of AER powder but increase in the kinetic property for chloride adsorption after the grinding process. The AER powder could absorb the chloride ion in the mortar quickly, and showed better chloride ion adsorption ability than the cement hydrates.

New experiment recipe for chloride penetration in concrete under water pressure

Yoon, In-Seok,Nam, Jin-Won Techno-Press 2016 Computers and Concrete, An International Journal Vol.17 No.2

Chloride penetration is considered as a most crucial factor for the determination of the service life of concrete. A lot of experimental tools for the chloride penetration into concrete have been developed, however, the mechanism was based on only diffusion, although permeability is also main driving forces for the chloride penetration. Permeation reacts on submerged concrete impacting for short to long term durability while capillary suction occurs on only dried concrete for very early time. Furthermore, hydrostatic pressure increases in proportional to measured depth from the surface of water because of the increasing weight of water exerting downward force from above. It is thought, therefore, that the water pressure has a great influence on the chloride penetration and thereby on the service life of marine concrete. In this study, new experiment is designed to examine the effect of water pressure on chloride penetration in concrete quantitatively. As an experiment result, pressure leaded a quick chlorides penetration by a certain depth, while diffusion induced chlorides to penetrate inward slowly. Therefore, it was concluded that chloride should penetrates significantly by water pressure and the phenomena should be accelerated for concrete exposed to deep sea. The research is expected as a framework to define the service life of submerged concrete with water pressure and compute water permeability coefficient of cementitious materials.

염화물 고정화를 고려한 철근 콘크리트 구조물의 내구수명 예측

이창수,박종혁,김영욱 한국방재학회 2010 한국방재학회논문집 Vol.10 No.1

Chloride-induced corrosion of steel bars in concrete exposed to marine environments has become one of the major causes of deterioration in many important facilities made of reinforced concrete. A study on chloride penetration in concrete has developed through long period exposure test along seawater, assesment of chloride ion diffusion by electrochemical techniques and so on. However, reasonable and exclusive chloride penetration model considering concrete material properties with mixture, degree of hydration, binding capacity has not been established. Therefore, in this paper, chloride penetration analysis of non-steady state is accomplished with material properties of concrete. Comparing with the results of analysis and chloride ponding test, we could accept the effect of binding capacity on chloride penetration in concrete and these results could be applied to a service life prediction of R.C. structures submerged in seawater. Therefore, there are 20~40% differences of service life to SHRP prediction. 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.

Resistance of coal bottom ash mortar against the coupled deterioration of carbonation and chloride penetration

Jang, J.G.,Kim, H.J.,Kim, H.K.,Lee, H.K. Elsevier Ltd 2016 Materials & Design Vol.93 No.-

<P>This paper investigated the resistance of bottom ash mortar against the coupled deterioration of carbonation and chloride penetration. To evaluate the resistance of the mortar, a comparative study was conducted with variables of ordinary mortar, lightweight mortar using expanded shale, fly ash cement mortar, and slag cement mortar. Test results showed that a combination of carbonation and chloride penetration accelerated the rate of chloride penetration into the mortar regardless of the mortar type. The replacement of sand with bottom ash moderated the penetration depth of chloride under coupled-deterioration environments, while the overall penetrated-chloride contents showed no significant differences. It can be concluded in a coupled-deterioration environment that the chloride resistance of the bottom ash mortar was greater than that of both ordinary mortar and lightweight mortar. The type of cement paste on the surface of a carbonated mortar had a governing impact on the chloride penetration. (C) 2015 Elsevier Ltd. All rights reserved.</P>

Compressive Strength and Chloride Resistance of Metakaolin Concrete

G. Dhinakaran,S. Thilgavathi,J. Venkataramana 대한토목학회 2012 KSCE JOURNAL OF CIVIL ENGINEERING Vol.16 No.7

In the present research work, investigations were carried out to improve the performance of concrete in terms of strength and resistance to chloride-ion-penetration by incorporating metakaolin (MK) as mineral admixture in concrete. Parametric study was carried out by considering w/cm ratio, various percentage of MK and age of concrete as parameters to understand the effect of each parameter. The study was conducted for different water-to-cement metakaolin ratio (w/cm) ratios of 0.32, 0.35, 0.4 and 0.5. The MK proportion was varied from 0 to 15% with an increment of 5% and ages of concrete from 3 to 90 days were considered and experiments performed accordingly. The effects of above said parameters on the various properties of concrete such as workability,compressive strength, chloride penetrability (Rapid chloride permeability test as per ASTM C 1202), pH of concrete and depth of penetration of chloride ions were investigated, and the results of MK concrete were compared with the conventional concrete. From the results, it was observed that MK concrete showed greater strength for higher w/cm ratios (0.4 and 0.5) and its resistance to chloride ion penetration was more or less consistent for all w/cm ratios and the optimal amount of MK resulted significant reduction in chloride ion penetration. A Multiple non-linear regression analysis was used to develop a statistical model to predict the strength and found to have good correlation between the observed and predicted values. It was concluded that the concrete developed in this study have significant potential for use on real time projects.

A highly sensitive ultrathin-film iron corrosion sensor encapsulated by an anion exchange membrane embedded in mortar

Im, Healin,Lee, Yunsu,Kim, Do Hyeong,Inturu, Omkaram,Liu, Na,Lee, Sungho,Kwon, Seung-Jun,Lee, Han-Seung,Kim, Sunkook Elsevier BV 2017 Construction and Building Materials Vol.156 No.-

<P><B>Abstract</B></P> <P>In this paper, an embedded ultrathin-film iron (Fe) corrosion sensor passivated with an anion-exchange membrane is developed to reveal the extent of corrosion tendency in reinforced concrete. Rebar in reinforced concrete is mainly corroded due to penetration of chloride ions which are one of the most dominant degradation factor for reinforced concrete. An effective method to monitor the extent of corrosion is to determine the positions where the chloride ions are present beyond the chloride threshold level (CTL). The sensors consist of ultrathin-film iron (Fe) layers deposited on the PET substrate, Au lines as electrode connection lines, and anion exchange membrane encasing the sensor. As the chloride ions exist near Fe layer of sensors, as if rebar has been corroded in reinforced concrete, the macro cells which occur relatively low anode and high cathode with somehow distance between them are made up and pitting corrosion accelerates. The pitting corrosion on the Fe layer of sensor induces the variation of electrical properties, which indicates the corrosion level using variations of resistance (<I>R</I>) and electrical response (<I>R</I>/<I>R<SUB>0</SUB> </I>). To protect the sensor from mechanical and chemical stimuli in a concrete, sensors are encapsulated with an anion exchange membrane that functions not only as a protector, but also as a selector of anions including chloride ions among degradation factors. Therefore, by embedding sensors at every 10 mm depth from the surface of reinforced concrete, we can monitor the corrosion tendency causing penetration of chloride ions with respect to depth. Through the variation of electrical properties in sensors, the velocity of corrosion ( Δ R · R 0 - 1 · <SUP> t - 1 </SUP> ) is suggested as a new parameter, which shows the tendency for corrosion under the surrounding conditions. To confirm the relationship between corrosion velocity as determined by the sensor and the concentration of diffused chloride ions, the chloride concentration in mortar is measured. The developed sensors in this paper are effective to sensitively and accurately monitor the corrosion level of concrete.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Embedding sensors in a fresh mortar. </LI> <LI> Chlorides permeating toward anion exchange membrane of sensors. </LI> <LI> Corroding iron channel by diffused chlorides. </LI> <LI> Occurring rapid variation in electrical changes of sensors by diffused chlorides. </LI> <LI> Indicating corrosion velocities at the spot based on the surrounding condition. </LI> </UL> </P>

압력조건을 고려한 콘크리트의 염화물이온 침투 장치 개발

김경태 ( Kim Gyeong-tae ),김규용 ( Kim Gyu-yong ),이상규 ( Lee Sang-kyu ),황의철 ( Hwang Eui-chul ),손민재 ( Son Min Jae ),남정수 ( Nam Jeong-soo ) 한국건축시공학회 2018 한국건축시공학회 학술발표대회 논문집 Vol.18 No.1

In this study, the device was developed for evaluating the effect of pressure on chloride ion penetration of concrete. And chloride-ion penetration depth and water soluble chloride contents was evaluated concrete using ordinary portland cement and blast-furnace slag cement using developed device. As a result, chloride ion penetration of concrete was promoted according to the action of pressure and the exposure period. and the incorporation of blast-furnace slag was effective for chloride attack resistibility under pressure.

Evaluation of Fiber and Blast Furnace Slag Concrete Chloride Penetration through Computer Simulation

Kim, Dong-Hun,Petia, Staneva,Lim, Nam-Gi The Korean Institute of Building Construction 2011 한국건축시공학회지 Vol.11 No.4

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.

Evaluation of Fiber and Blast Furnace Slag Concrete Chloride Penetration through Computer Simulation

김동훈,stameva. petoa,임남기 한국건축시공학회 2011 한국건축시공학회지 Vol.11 No.4

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.