콘크리트의 동결융해 저항성 추정을 위한 표면 거칠기 및 이미지 분석의 적용성

Abstract

As part of a research dedicated to the field evaluation of the durability of concrete subjected to freezing-thawing, this study analyzes therelationship between the surface roughness and the relative dynamic elastic modulus through image analysis. Four mix compositions withwater-to-binder ratios (W/B) of 40%, 50%, 60% and 70% and without AE agent were considered to provoke early freezing. The basic physical propertiesof the mixes including the relative dynamic elastic modulus and the compressive strength were first evaluated experimentally according to W/B. Then,tests were performed to measure the surface roughness followed by photographs and SEM image analysis. The measured surface roughness tendedto increase with larger number of freezing-thawing cycles regardless of W/B. The relative dynamic elastic modulus appeared to increase gradually withthe number of cycles for the relatively denser mixes with W/B of 40% and 50%. Besides, the surface roughness increased only at rupture for the mixeswith W/B of 60% and 70%. Moreover, the analysis of the photographs of the surface of the mixes with W/B of 40% and 50% revealed that the degradationprogressed gradually from the surface with the freezing-thawing cycles. However, for the mixes with W/B of 60% and 70%, apparent change of thesurface remained very insignificant until rupture at which damage like cracking could be observed. Consequently, the analysis of surface photographor the measurement of the surface roughness presented some limitation in assessing the degree of freezing-thawing-induced degradation in case ofrelatively porous specimens. On the other hand, the photograph and surface roughness appeared to be sufficient for assessing such degradation forthe mixes with W/B of 40% and 50%. Accordingly, the image of the surface and the surface roughness are potentially applicable on site for the assessmentof freezing-thawing damages in relatively dense mixes.