한국지반공학회논문집 (Journal of the Korean Geotechnical Society)

  • 제36권11호
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  • Pages.97-106
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  • 2020
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  • 1229-2427(pISSN)
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  • 2288-646X(eISSN)
한국지반공학회 (Korean Geotechnical Society)
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수화 반응에 따른 MgO-모래 혼합물의 팽창 특성 및 전단 거동 변화

Effect of Hydration on Swelling Properties and Shear Strength Behavior of MgO-sand Mixture

  • 이지환 (고려대학교 건축사회환경공학부) ;
  • 윤보영 (고려대학교 건축사회환경공학부) ;
  • 추현욱 (경희대학교 사회기반시스템공학과) ;
  • 이우진 (고려대학교 건축사회환경공학부) ;
  • 이창호 (전남대학교 토목공학과)
  • Lee, Jihwan (School of Civil, Environmental and Architectural Engrg., Korea Univ.) ;
  • Yoon, Boyoung (School of Civil, Environmental and Architectural Engrg., Korea Univ.) ;
  • Choo, Hyunwook (Dept. of Civil Engrg., Kyung hee Univ.) ;
  • Lee, Woojin (School of Civil, Environmental and Architectural Engrg., Korea Univ.) ;
  • Lee, Changho (Dept. of Civil Engrg., Chonnam National Univ.)
  • 투고 : 2020.10.06
  • 심사 : 2020.10.20
  • 발행 : 2020.11.30
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초록

본 연구에서는 산화 마그네슘(MgO) 무게비에 따른 WMgO/WTotal=0, 30, 50, 70, 100%) MgO-모래 혼합물의 팽창특성과 수화 반응 전·후 전단거동을 비교하였다. 시료는 MgO 함량이 높은 내화벽돌을 파쇄하여 모래와 혼합하여 조성하였다. MgO는 수화반응 후 Mg(OH)2로 분화되어 비중 및 입자 크기가 감소하였다. 미세구조 관찰과 X선 회절분석을 통해 MgO는 정육면체 구조인 Periclase에서 수화반응 후에 육각형 결정 구조인 Brucite로 변화하는 것을 확인하였다. MgO 함량이 증가함에 따라 팽창압과 팽창량은 증가하는 것으로 나타났다. 생성된 Mg(OH)2가 모래 입자 사이의 공극을 주로 채우게되는 MgO 함량 30% 시료는 팽창압과 팽창량이 상대적으로 매우 낮게 측정되었고, MgO 50% 이상의 시료에서는 Mg(OH)2가 모래 입자 사이의 공극을 채우고 난 후 모래 입자 또는 다른 Mg(OH)2를 밀어내기 때문에 팽창압과 팽창량이 급격히 증가하는 양상을 보였다. 직접전단시험 결과 수화반응 전 혼합물은 높은 MgO 함량에서는 부피 팽창거동을 보였고 낮은 MgO 함량에서는 부피 수축거동을 보였다. 그러나 수화반응 후 혼합물은 모두 부피 수축거동을 보였다. 수화반응 후 정규화된 전단강도의 한계 세립질 함량 (Fth)은 약 60% Mg(OH)2 비율로 나타났다.

Swelling properties and shear strength behavior of MgO-Sand mixtures with hydration procese of MgO are compared according to different MgO contents (WMgO/WTotal=0, 30, 50, 70, 100%) in this study. The specimens are prepared by mixing with crushed MgO refractory bricks and silica sand. After hydration, the particle size and the specific gravity of MgO were decreases. Through microstructure observation and X-ray diffraction analysis, it is confirmed that MgO changes from the cubic structure of Periclase to the hexagonal cubic structure of Brucite after hydration. As the MgO content increases, both swelling rate and swelling pressure of the mixtures increase. WMgO/WTotal=30% specimen shows relatively low swelling pressure and swelling rate because produced Mg(OH)2 mainly fills the pores between sand particles. However, in the case of MgO more than 50%, swelling pressure and swelling rate increase significantly because Mg(OH)2 fills the pores of sand particles at first and then either pushes out sand particles or Mg(OH)2 particles after filling the pores. As a result of the direct shear test, before hydration, the mixtures show a dilative behavior on high MgO contents and a contractive behavior on low MgO contents. However, after hydration, the behavior of all mixtures changes to contractive behavior. The threshold fraction of fine (i.e., Mg(OH)2) contents of the hydrated MgO-Sand mixtures reveals approximately 60% compared with normalized shear strength.

키워드

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