• Analytical Science and Technology
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• v.14 no.4
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• pp.364-370
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• 2001

The corrosion behaviors of reinforcing steels were investigated under chloride ion contained in cement mortar including gypsum by the implementation of half cell potential measurement, EPMA analysis, exterior features, weight loss and extraction experiment. The acceleration test equipment accelerated corrosion of mild steel bar in a short period of time. From observing the exterior features and weight loss, we could evaluate the measure of corrosion. Also, from the extraction experiment of ${SO_4}^{2-}$ with $Cl^-$ ions contained in the ceramic mortar, we concluded that ${SO_4}^{2-}$ ion affected more on the corrosion mechanism in comparison to pH.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.4
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• pp.1095-1104
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• 2014

This paper presents the results of experimental work on both strength characteristics and durability of concrete or mortar having 50% ground granulate blastfurnace slag(GBS) with different fineness levels (4,450, 6,000 and $8,000cm^2/g$). Compressive and split tensile strength test results indicated that the concrete with a higher fineness level of GBS exhibited a better strength development due to the acceleration of latent hydraulic property at the later curing stage compared with ordinary portland cement concrete. Meanwhile, it was found that a higher fineness level of GBS showed some negative effects on the resistance against freezing-thawing action. However, incorporation of GBS to concrete, irrespective of fineness levels, significantly enhanced the chloride ions penetration resistance. The resistance against sulfate attack of mortar with GBS was greatly dependent on the attacking sources from sulfate environments.

• The Journal of Engineering Geology
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• v.26 no.1
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• pp.79-85
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• 2016

A concrete silo plays an important role in subsurface low- and intermediate-level waste facilities (LILW) by limiting the release of radionuclides from the silo geosphere. However, due to several physical and chemical processes the performance of the concrete structure decreases over time and consequently the concrete loses its effectiveness as a barrier against groundwater inflow and the release of radionuclides. Although a number of processes are responsible for degradation of the silo concrete, it is determined that the main cause is corrosion of the reinforcing steel. Therefore, the time it takes for the silo concrete to fail is calculated based on two factors: the initiation time of corrosion, defined as the time it takes for chloride ions to penetrate through the concrete cover, and the propagation time of corrosion. This paper aims to estimate the time taken for concrete to fail in a LILW disposal facility. Based on the United States Department of Energy (DOE) approach, which indicates that concrete fails completely once 50% of the volume of the reinforcing steel corrodes, the corrosion propagation time is calculated to be 640 years, which is the time it takes for corrosion to penetrate 0.640 cm into the reinforcing steel. In addition to the corrosion propagation time, a diffusion equation is used to calculate the initiation time of corrosion, yielding a time of 1284 years, which post-dates the closure time of the LILW disposal facility if we also consider the 640 years of corrosion propagation. The electrochemical conditions of the passive rebar surface were modified using an acceleration method. This is a useful approach because it can reduce the test time significantly by accelerating the transport of chlorides. Using instrumental analysis, the physicochemical properties of corrosion products were determined, thereby confirming that corrosion occurred, although we did not observe significant cracks in, or expansion of, the concrete. These results are consistent with those of Smartet al., 2006 who reported that corrosion products are easily compressed, meaning that cracks cannot be discerned by eye. Therefore, it is worth noting that rebar corrosion does not strongly influence the hydraulic conductivity of the concrete.

• Journal of the Korea Institute of Building Construction
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• v.22 no.6
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• pp.651-662
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• 2022

The electrochemical impedance spectroscopy(EIS) method was used to evaluate the concrete deterioration process related to chloride-induced steel corrosion with various corrosion levels(initiation, rust propagation and acceleration periods). The impressed current technique, with four total current levels of 0C, 13C, 65C and 130C, was used to accelerate steel corrosion in concrete cylinder samples with w/c ratio of 0.4, 0.5, and 0.6, immersed in a 0.5M NaCl solution. A series of EIS measurements was performed to monitor concrete deterioration during the accelerated corrosion test in this study. Some critical parameters of the equivalent circuit were obtained through the EIS analysis. It was observed that the charge transfer resistance(R_c) dropped sharply as the impressed current increased from 0C to 13C, indicating a value of approximately 10kΩcm². However, the sensitivity of R_c significantly decreased when the impressed current was further increased from 13C to 130C after corrosion of steel had been initiated. Meanwhile, the double-layer capacitance value(C_dl) linearly increased from 50×10^-6μF/cm² to 250×10^-6μF/cm² as the impressed current in creased from 0C to 130C. The results in this study showed that monitoring C_dl is an effective measurement parameter for evaluating the progress of internal concrete damages(de-bonding between steel and concrete, micro-cracks, and surface-breaking cracks) induced by steel corrosion. The findings of this study provide a fundamental basis for developing an embedded sensor and signal interpretation method for monitoring concrete deterioration due to steel corrosion at various corrosion levels.