• Journal of the Korea Institute of Building Construction
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• v.22 no.6
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• pp.553-564
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• 2022

Concrete is a representative composite material that shows excellent performance in the construction field. However, it is a brittle and nonhomogeneous material and exhibits weak behavior against bending and tensile forces. To compensate for such weakens, fiber reinforcement has been utilized, and steel fiber has been recognized as one of the best material for such purpose. However, steel fiber can seriously affect the durability of concrete exposed to the marine environment due to the corrosion caused by chlorine ions. This study intended to evaluate the mechanical performance of steel fiber reinforce concrete during and after repeated wet/dry cycles in salt solution. According to the experimental results, there was no reduction in the relative dynamic modulus of concrete during the repeated wet/dry cycles in salt solution for 37 weeks. Flexural strength was not decreased after completion of repeated wet/dry cycles in salt solution. There was no sign of corrosion in steel fibers after visual observation of fractured surface. However, the flexural toughness was decreased, and this is because about half of the concrete specimen showed failure before reaching the maximum displacement of 3 mm. Although repeated wet/dry cycles in salt solution did not cause cracks in concrete through corrosion of steel fibers, specific attention is required because it can reduce flexural toughness of steel fiber reinforced concrete.

• Korean Chemical Engineering Research
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• v.59 no.3
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• pp.339-344
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• 2021

In order to improve the PEMFC (Proton Exchange Membrane Fuel Cell) durability, it is important to accurately evaluate the durability of the membrane in a short time. Recently, DOE (Department of Energy) reported a protocol that combines the chemical and mechanical durability of membranes to evaluate them effectively. This protocol applies chemical/mechanical deterioration to the membrane by repeating wet/dry while OCV (Open Circuit Voltage) holding. The problem of this protocol is that it is highly affected by electrode degradation due to change cycles in OCV and that the evaluation time is long. By using oxygen instead of air as the cathode gas while leaving the other conditions of the DOE protocol as it is, the durability evaluation time could be reduced from 408 hours to 144 hours. By reducing the number of voltage change cycles to 1/3, the electrode degradation due to the voltage change cycle was reduced to 1/12 when oxygen was used compared to air at the end, thereby enabling more accurate evaluation of polymer membrane durability.