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Engineering Characteristics of Cemented Sand with Microorganism Using Eggshell as Calcium Source

달걀껍질을 칼슘원으로 사용한 미생물 고결 모래의 공학적 특성

  • Received : 2016.02.16
  • Accepted : 2016.05.01
  • Published : 2016.05.31

Abstract

A calcium source is necessary for calcite precipitation within soil particles by microbial decomposition of urea and a calcium chloride is usually used. The harmful environmental impact of calcium chloride on road, ground and plants is severe. In this study, an eggshell with vinegar is investigated for an environmental-friendly calcium source. Urea-decomposing microorganism and eggshell or calcium chloride as a calcium source are mixed with Ottawa sand to precipitate calcite. Then, the cemented sand with calcite is tested for calcite precipitation, permeability and unconfined compressive strength. A specimen is prepared by loose Ottawa sand in a size of 5 cm in diameter and 10 cm in height. A urea solution with Sporosarcina pasteurii and two different calcium sources is injected into the specimen once a day for 30 days. Calcite precipitated at average of 7.2% on the specimen with eggshell as a calcium source, which was 1.2 times more than that with calcium chloride. The permeability of a specimen with eggshell was at average of 3.82E-5 cm/s, which was 7.7 times lower than that with calcium chloride. Unconfined compressive strength of a specimen with eggshell was at average of 387 kPa, which was 1.2 times higher than that with calcium chloride. As more calcite precipitated, the strength increased while the permeability decreased, regardless of calcium sources.

요소 분해 미생물을 이용하여 흙 입자 사이에 칼사이트를 석출시킬 때 칼슘원이 필요하며, 일반적으로 염화칼슘을 칼슘원으로 사용하고 있다. 염화칼슘은 도로, 지반 및 주변 식물에 부작용을 일으키므로 본 연구에서는 버려지는 달걀껍질을 사용한 칼슘원을 개발하고자 하였다. 미생물에 기존 칼슘원인 염화칼슘 또는 식초로 달걀껍질을 분해하여 얻은 새로운 칼슘원을 혼합하여 모래 입자 사이에 칼사이트를 생성시킨 다음, 고결모래의 칼사이트 생성량, 투수계수 및 일축압축강도를 비교 분석하였다. 공시체 제작은 느슨한 상태의 Ottawa모래로 직경 5cm, 높이 10cm 공시체를 만든 다음 Sporosarcina pasteurii 미생물을 포함한 요소와 두 종류의 칼슘원을 1일 1회씩 30일 동안 주입하여 제작하였다. 칼슘원으로 달걀껍질을 사용한 경우 칼사이트 생성량은 평균 7.2%로 염화칼슘을 사용한 경우보다 1.2배 높았다. 또한 달걀껍질을 사용하여 고결시킨 공시체의 투수계수는 평균 3.82E-5cm/s로 7.7배 정도 감소하였으며, 일축압축강도는 평균 387kPa로 염화칼슘을 사용한 경우보다 1.2배 높았다. 한편, 칼슘원에 관계없이 칼사이트 생성량이 증가할수록 강도는 증가하고 투수계수는 감소하는 경향을 보였다.

Keywords

References

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