KSCE Journal of Civil and Environmental Engineering Research (대한토목학회논문집)

Korean Society of Civil Engeneers (대한토목학회)
권호 표지

A Study on Rermeability Characteristics of Carbonated Concrete Considering Micro Pore Structure

공극구조를 고려한 탄산화된 콘크리트의 투수 특성에 대한 연구

Kwon, Seung-Jun;Song, Ha-Won;Park, Chan-Kyu;Byun, Keun-Joo
권성준;송하원;박찬규;변근주

  • Published : 2005.05.31

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Abstract

Permeability of concrete is considered as an index to show durability resistance of concrete because deteriorations like chloride penetration and carbonation mainly depend on the moisture transfer in pore structure of concrete. During the carbonation process, the pore structure inside concrete is changing with consumed $Ca(OH)_{2}$ and produced $CaCO_{3}$ and the permeability of concrete is also changing mainly due to the change of porosity in cement paste. Specially for underground RC structures, the interior concrete surface may be exposed to carbonation and the exterior concrete surface exposed to wet soil or underground water. However, research on permeability characteristics of concrete considering the carbonation and its micro-structured information is very much limited. In this study, the permeability in non-carbonated concrete is firstly derived by applying a micro structure formation model into carbonated cement paste in early-aged concrete without consideration of effect of coarse aggregates and the interfacial transition zone and then permeability in carbonated mortar is derived as a function of carbonation depth and changed porosity using the results for non-carbonated mortar. The permeability obtained from the micro pore structure formation model and permeability modeling of carbonated concrete is verified with the results of accelerated carbonation test and water penetration test on cement mortar. The results show that in non-carbonated specimens, the permeability coefficients measured are 1.91 ${\times}$ $1^{10}$ m/s(W/C : 65%) and 8.35 ${\times}$ $10^{11}$ m/s (W/C : 55%), respectively, and both of them are expected to be finally decreased to almost 25% of those non-carbonated specimens.

염해나 탄산화와 같은 열화현상은 주로 콘크리트 내의 수분이동에 기인하므로 콘크리트의 투수성은 콘크리트의 내구적 저항성을 나타내는 지표로 여겨지고 있다. 탄산화 반응이 진행되는 동안 콘크리트 내부에 존재하는 시멘트풀 모재의 공극구조는 소모된 수산화칼슘과 생성된 탄산칼슘에 따라 변화하게 되며, 이에따라 콘크리트의 투수성이 변화하게 된다. 특히 지하 RC 구조물과 같은 경우, 내부는 탄산화에 노출되어 있으며, 외부는 젖은 토양이나 지하수에 노출되어 있는데 탄산화 및 이에 따른 공극구조변화를 고려한 투수특성에 대한 연구는 매우 제한적이다. 본 논문에서는 초기재령에서의 미세공극구조 형성모델을 먼저 탄산화 되지 않은 시멘트 풀에 적용한 뒤, 굵은골재 및 천이영역의 영향을 고려하지 않고 탄산화되지 않은 콘크리트에 대한 투수계수를 도출하였다. 이후 탄산화된 시멘트 모르타르의 투수계수를 탄산화 되지 않은 모르타르의 실험결과를 이용하여 탄산화깊이와 변화된 공극률의 함수로 도출하였다. 미세공극구조 형성모델 및 탄산화된 콘크리트의 투수계수 모델링을 통해 도출된 결과는 촉진 탄산화 실험과 저압투수실험에 따른 투수계수의 평가를 통하여 검증하였다. 탄산화가 진행되지 않은 시편의 투수계수는 각각 1.91${\times}$$10^{10}$ m/s(물-시멘트비 : 65%), 8.35${\times}$$10^{11}$ m/s(물-시멘트비 : 55%)이었으며 최종적으로 완전히 탄산화가 되었을 경우의 투수계수는 초기의 25%정도 수준으로 예상되었다.

Keywords

References

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