황산염을 함유한 생석회와 화학첨가제 혼합토의 팽창특성

Abstract

최근 많이 건설중인 도로에서 연약지반을 노상토로 사용하게 될 경우, 공학적으로 많은 문제점이 발생되기 때문에 생석회, 시멘트 등의 여러 가지 화학첨가제를 첨가하여 지반을 개량하게 된다. 특히 생석회에 의한 토질안정처리공법에서 주된 반응은 생석회와 흙 사이에 장기간에 걸쳐 일어나는 포졸란 반응이며, 산성화된 우수 및 공장의 폐수로 오염된 토양 속의 황산염과 결합하여 토질안정처리의 많은 문제점이 발생되고 있다. 도로의 기층재료로 사용된 생석회 혼합토는 흙 속의 황산염과 반응하여 Ettringite, Thaumasite, Gypsum과 같은 팽창성 반응생성물을 생성하여, 도로의 균열 등 악영향을 미친다. 따라서, 본 연구에서는 생석회와 화학첨가제(CaCl₂, CaSO₄, Fe₂O₃)를 혼합하여 산성화된 우수나 공장지대의 오염된 폐수 속에 포함된 황산염에 대한 영향을 조사하였다. 연구결과, 황산염은 생석회 혼합토의 팽창특성을 변화시키는 것으로 나타났다. 팽창특성은 간극수의 pH가 낮을수록 팽창성이 증가하였으며, CaSO₄를 첨가한 생석회 혼합토의 팽창성이 큰 것으로 나타났다. 팽창성의 증가는 황산염과 반응하여 생성된 침상의 Ettringite의 생성에 기인한 것임을 확인할 수 있었다.

Lime has been extensively utilized to stabilize the weak and soft compressible clay deposits. It has been recently reported that the presence of sulphate causes abnormal volume changes in lime-stabilized soils. Volume change in lime-stabilized soils can take place due to ettringite, thaumasite, and gypsum, which are complex calcium-silicate-hydroxide-sulphate-carbonate-hydrate minerals. Sulphate compounds cause a variety of serious geotechnical hazards such as swell pressure and damages to light structures and pavements.

This paper discusses the influence of sulphate on sulplus soil specimens treated with lime and chemical additives(CaCl₂, CaSO₄, Fe₂O₃). The main objective of this paper is to estimate the physical behavior of lime-treated sulplus soils after curing periods of up to 60 days. The physical and mechanical characteristics were explained by means of a laboratory study. The formation of sulphate compounds due to soil-lime and sulphate reactions were identified by X-Ray Diffraction(XRD) and Scanning Electron Microscope(SEM).

The results showed that the sulphate increased swelling properties of soils. Theswelling properties development is probably related to the needle-like crystals which were able to be observed by SEM.

Lime has been extensively utilized to stabilize the weak and soft compressible clay deposits. It has been recently reported that the presence of sulphate causes abnormal volume changes in lime-stabilized soils. Volume change in lime-stabilized soils can take place due to ettringite, thaumasite, and gypsum, which are complex calcium-silicate-hydroxide-sulphate-carbonate-hydrate minerals. Sulphate compounds cause a variety of serious geotechnical hazards such as swell pressure and damages to light structures and pavements.

This paper discusses the influence of sulphate on sulplus soil specimens treated with lime and chemical additives(CaCl₂, CaSO₄, Fe₂O₃). The main objective of this paper is to estimate the physical behavior of lime-treated sulplus soils after curing periods of up to 60 days. The physical and mechanical characteristics were explained by means of a laboratory study. The formation of sulphate compounds due to soil-lime and sulphate reactions were identified by X-Ray Diffraction(XRD) and Scanning Electron Microscope(SEM).

The results showed that the sulphate increased swelling properties of soils. Theswelling properties development is probably related to the needle-like crystals which were able to be observed by SEM.