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Title |
Evaluation of Freeze-Thaw Damage on Concrete Using Nonlinear Ultrasound
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Authors |
최하진(Ha-Jin Choi) ; 김률리(Ryul-Ri Kim) ; 이종석(Jong-Suk Lee) ; 민지영(Ji-Young Min) |
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DOI |
https://doi.org/10.11112/jksmi.2021.25.4.56 |
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Keywords |
콘크리트; 동결융해; 초음파; 비선형성; 빠른 동특성 Concrete; Freeze-thaw; Ultrasound; Nonlinear; Fast dynamic |
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Abstract |
Leakage due to deterioration and damage is one of the major causes of volume change by freezing and thawing, and it leads micro-crackingand surface scaling in concrete structures. The deterioration of damaged concrete accelerates with the chloride attack. Thus, in the detailed guidelinesfor facility performance evaluation (2020), the quality of cover concrete and the freeze-thaw (FT) repetition cycle were newly suggested for concretedurability assessment. The quality of cover concrete should be evaluated by the rebound hammer test and the FT repetition cycle should be also consideredin the deterioration environmental assessment. This study suggested the application of fast dynamic based nonlinear ultrasound method to monitorinitial micro-scale damage under freezing and thawing environment. Concrete specimens were fabricated with different water-cement ratios (40%,60%) and air contents (1.5% and 3.0%). The compressive strength, rebound number, relative dynamic modulus, and nonlinear ultrasound weremeasured with different FT cycles. The scanning electron microscopy was also performed to investigate the micro-scale FT damage. As a result, boththe rebound number and the relative dynamic modulus had difficulty to detect early damage but the proposed method showed a potential to detectinitial micro-scale damage and predict the FT resistance performance of concrete.
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