Abstract
Soils exhibit undesirable volume changes when exposed to high concentrations of acids, which is manifested most frequently in the beds of foundations of industrial establishments associated with their production or use. However, control of this phenomenon has received less attention than it deserves. This paper aims to investigate the mineralogical and micro-structural changes occurred during the volume change behavior of phosphogypsum treated clayey soils contaminated with sulfuric acid and phosphoric acid solutions. Oedometer test results showed high swelling and low compressibility for acid contaminated soils than that of water. The change in microstructure towards flocculated fabric along with mineralogical transformations are responsible for the volume changes in soils. The mineralogical changes that affected the volume change behavior are discussed with FT-IR, XRD and SEM analysis. Phosphogypsum treatment was found to be effective in controlling volume changes in soils with phosphoric acid, whereas in the case of sulfuric acid found to be futile.
Highlights
Industrial chemicals often leak into soil or rocks resulting in contamination (Assa’ad 1998; Al-Omari et al 2007)
It has been reported that sulfuric acid contaminated soils reveal high swelling which resulted in distress to the structures built on them
The concentration of sulfuric acid and phosphoric acid used for different industrial purposes ranges from 12–40 N and when these acid solutions leak into the subsoil and are diluted, the concentration may range within 1–4 N (Sivapullaiah et al 2009)
Summary
Industrial chemicals often leak into soil or rocks resulting in contamination (Assa’ad 1998; Al-Omari et al 2007). Soil contamination problems pose new challenges to the current geotechnical engineering practice as it involves complex chemical reactions between soil and contaminant. It requires a better understanding of compositional characteristics of soils and their relation to the long-term physical and chemical properties that control soil behavior under changed and extreme environmental conditions (Mitchell 1993). Failures of structures and tilting of acid storage tanks in fertilizer industry due to accidental spillage or leakages of phosphoric acid with the subsequent heaving of foundation soils have been investigated in India (Sridharan et al 1981; Rao, Reddy 1997) and other countries (Grant et al 1974; Joshi et al 1994; Assa’ad 1998; Al-Omari et al 2007). It has been reported that sulfuric acid contaminated soils reveal high swelling which resulted in distress to the structures built on them
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