CaAl2O4-CaAl4O7 혼입 포틀랜드 시멘트 결합재의 염소이온 고정 특성
Chloride Binding Properties of Portland Cement Binder Incorporating CaAl2O4-CaAl4O7
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초록
본 연구는 철근콘크리트 구조물의 염해 내구성 향상의 일환으로써, 보통 포틀랜드 시멘트에 실험체별 다른 비율의 칼슘 알루미네이트 시멘트와 합성 CA2를 혼입하여 혼입 비율에 따른 염소이온 고정능력을 평가하였다. 침지 후 실험체의 물리·화학적 특성을 압축강도, 공극구조, 수화물 분석으로 염소이온침투깊이를 EPMA를 통하여 고찰하였다. 클링커 조성에 CA가 34%미만일 경우 실험체의 조밀성이나 강도 발현 양상이 구조재료로서 사용 제한이 없을 것이라고 판단되었으며 CAC와 CA2를 5:5비율로 혼입하여 실험체에 치환한 실험체가 CAC 혹은CA2만 치환한 실험체보다 염소이온 침투억제능력 과 AFm상 및 프리델 염 생성이 높은 것으로 확인할 수 있었다. 결과적으로, 시멘트 페이스트 대비 칼슘 알루미네이트 클링커 치환율이 증가함에 따라 일반적으로 염소이온 고정능력이 향상하였고, CA-CA2비율에 따라 염소이온 고정능력 및 염소이온 침투억제 능력에 차이가 있음을 확인할 수 있었다. 실험 범위 내에서 CA-CA2비율이 39:60이며 시멘트 페이스트 대비 10% 치환한 실험체인 M 10 가 가장 우수한 것으로 나타났다.
Abstract
This study conducted to understand effects of CA (CaAl2O4) and CA2 (CaAl4O7) ratio on chloride binding ability and compressive strengthand pore structure of cement mortar incorporating mixture of CA and CA2. The Portland cement based specimens were mixed with the clinkers CAand CA2, and these calcium aluminate clinker mixture were replaced 0, 5, 10% by weight of cement. After all the test specimens were cured for 28days under water curing, they were immersed in the distilled water and NaCl solution. As a result, 28 days compressive strength of all specimens wassimilar, and As the replacement ratio of calcium aluminate clinker in the specimen increased, Friedel’s salt production tended to increase. However,it was dependent on the amount of Al2O3 in the level of 5% replacement and CA ratio in the level of 10% replacement. Through equilibrium isothermresult, it was also indicated that as replacement ratio of calcium aluminate clinker in cement matrix increased, chloride binding capacity was improved,and chloride penetration was suppressed. In this study, the specimen replaced with 10% of the calcium aluminate clinker mixture (CA 39%, CA2 60%)was remarkable to control chloride attack. We figured out necessity to understand optimal CA/CA2 ratio to effectively apply CA2 as a sustainable buildingmaterial by improving the chloride binding ability in Portland cement based system.
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