• Journal of the Society of Disaster Information
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• v.7 no.1
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• pp.21-31
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• 2011

The objectives of this study is replaced Silicafume with Metakaolin that is used to lightweight concrete to better performance. So, this study made high-performance lightweight concrete using Metakaolin and characteristics of the fundamental properties and chloride ion diffusion. Consequently, it is compressive strength and chloride ion penetration resistance is lower than lightweight concrete using Silicafume, the performance of compressive strength contrast Silicafume is about 88 to 95%. Also, this study got a content result because the chloride ion penetration resistance showed the performance in around 80 to 90%. As a result, this study insist that replacement ratio of Metakaolin is suitable for 10 to 15%.Silicafume and Metakaolin have similar characteristics. In addition, it is similar to the performance of alternative materials is possible.

• 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.

• Architectural research
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• v.20 no.1
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• pp.27-34
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• 2018

To improve the chloride ingress resistance of concrete, slag is widely used as a mineral admixture in concrete industry. And currently, most of experimental investigations about non steady state diffusion tests of chloride penetration are started after four weeks standard curing of concrete. For slag blended concrete, during submerged chloride penetration tests periods, binder reaction proceeds continuously, and chloride diffusivity decreases. However, so far the dependence of chloride ingress on curing ages are not detailed considered. To address this disadvantage, this paper shows a numerical procedure to analyze simultaneously binder hydration reactions and chloride ion penetration process. First, using a slag blended cement hydration model, degree of reactions of binders, combined water, and capillary porosity of hardening blended concrete are determined. Second, the dependences of chloride diffusivity on capillary porosity of slag blended concrete are clarified. Third, by considering time dependent chloride diffusivity and surface chloride content, chloride penetration profiles in hardening concrete are calculated. The proposed prediction model is verified through chloride immersion penetration test results of concrete with different water to binder ratios and slag contents.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.395-398
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• 2005

In recent years, the applications of high-strength concrete have increased, and high-strength concrete has now been used in many parts of the world. The growth has been possible as a. result of recent developments in material technology and a demand for higher-strength concrete in Korea. In this study, we have an object to produce the ultra-high strength concrete(Super-Con) of over 100MPa with low price materials. First, the binders for Super-Con should be selected by the tests; setting time of paste, flow value and strength of mortar. From the test results, the binders are blended with ordinary portland cement, pulverized portland cement and silica fume. Fundamentally the compressive strength, frost resistance and chloride resistance are investigated.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.2
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• pp.50-59
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• 2020

Superabsorbent Polymer (SAP) expands inside concrete by absorbing water and contracts as it discharges water. Through this process, concrete can achieve the internal curing effect, but the space occupied by the expanded SAP remains as a void. In this study, the effects of SAP internal curing and voids were evaluated by evaluating the fundamental properties and chloride penetration resistance of SAP mixed concrete. Also, to evaluate the internal curing effect by SAP, the tests were carried out under water and sealed curing conditions, respectively. From the result, the compressive strength of water curing did not differ significantly according to the mixing ratio of SAP. In the case of sealed curing, however, the compressive strength tended to increase as the mixing ratio of SAP increased. The internal curing effect of sealed curing was considered to have influenced the increase in compressive strength. In the case of the chloride diffusion coefficient, the diffusion coefficient tended to decrease as the mixing ratio of SAP increased. In particular, as the sealed curing is applied, the chloride penetration resistance is further improved due to internal curing effect. If the curing conditions are different, it is considered inappropriate to estimate the chloride penetration resistance by the surface electrical resistivity.

• Advances in concrete construction
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• v.2 no.2
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• pp.109-123
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• 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.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.05a
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• pp.997-1002
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• 2001

There are two types of chloride in concrete; one is added as concrete materials' chloride when concrete's mixing, and .the other is penetrated from the air and sea water in the sea-shore area. These chlorides penetrate into concrete, and they are accumulated inside the concrete with aging. This study aimed to evaluate the chloride ion penetration resistance of concrete containing GGBFS in the sea-shore area. Therefore, the specimens made with the replacement ratios(0, 0.30, 0.45, 0.60) of GGBFS were put into 3% NaCl solution according to the chloride accelerating test of JCI-SC3, and then investigated the weight changes, compressive strength, chloride ion with the depths of the specimens by aging. The result is that the diffusion coefficient of chloride ion is decreased with the increase of replacement ratios when compared to OPC

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.3
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• pp.143-152
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• 2014

In this study, the sensor response and sensitivity is experimented and analyzed quantitatively by the line numbers of chlorine ion reaction type corrosion sensor that is developed. The sensor response of the developed corrosion sensor is verified with properties of chlorine ion. The multilineal sensor is shown a large resistance change more than the single line sensor by damage of the sensor. And, the resistance change of sensor is as large as high concentration of NaCl aqueous solution, the sensitivity of multilineal sensor is higher than single line sensor's, and the depth of sensor's location is as large as the increasing of resistance change time (cycle). These results suggest that, the developed corrosion sensor could sense corrosion reaction, sensor sensitivity and change of resistance for chloride ion. Especially, It was judged that 7 line sensor was the most superior for monitoring chloride ion immigration into concrete.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.521-524
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• 2008

The requirement for durability of concrete is increasing recently as a high-rise concrete structure is built. For this reason, the concern about high performance concrete is being high. Recently, metakaoline to be profitable in economical aspect as well as to have strength and durability of level similar to silica fume is evaluated highly as new admixture. In this study, the workability, the strength, the chloride resistance and the air-void structure more than 50${\mu}m$ are evaluated by comparing both metakaolin and silica fume. According to the results, when the metakaoline is compared with silica fume in properties of fresh concrete, it seems to the similar level of properties. Metakaoline concrete showed the highest value in the strength property. And, it is showed that replacement of the metakaoline more than 10% is superior than both silica fume and OPC in long and short-term chloride resistance. In conclusion, replacement of the metakaoline more than 10% is the most excellent performance in terms of strength and chloride resistance

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.5
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• pp.112-118
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• 2022

In this study, the diffusion characteristics were evaluated using the concrete mix design of nuclear safety-related structures. Among the concrete structures related to nuclear power safety, we selected the composition of intake and drainage structures that are immersed in seawater or located on the tidal platform and evaluated the chloride ion permeation resistance by compressive strength and electrical conductivity and the diffusion characteristics by immersion in salt water. analyzed. Compressive strength was measured on the 1st, 7th, 14th, 28th, 56th, and 91st days until the 91st day, which is the design standard strength of the nuclear power plant concrete structure, and chloride ion permeation resistance was evaluated on the 28th and 91st. After immersing the 28-day concrete specimens in salt water for 28 days, the diffusion coefficient was derived by collecting samples at different depths and analyzing the amount of chloride. As a result, it was found that after 28 days, the long-term strength enhancement effect of the nuclear power plant concrete mix with 20% fly ash replacement was higher than that of concrete using 100% ordinary Portland cement. It was also found that the nuclear power plant concrete mix has higher chloride ion permeation resistance, lower diffusion coefficient, and higher resistance to salt damage than the concrete mix using 100% ordinary Portland cement.