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GMCs stabilized/solidified Pb/Zn contaminated soil under different curing temperature: Physical and microstructural properties

Wang, Fei, Shen, Zhengtao, Liu, Rongqin, Zhang, Yunhui, Xu, Jian, Al-Tabbaa, Abir
Chemosphere 2020 v.239
United States Environmental Protection Agency, X-ray diffraction, adsorption, calcium silicate, compression strength, furnaces, gels, hydrotalcite, lead, polluted soils, scanning electron microscopy, slags, soil remediation, solidification, temperature, zinc
Stabilization/Solidification (S/S) has been widely used in soil remediation to both improve physical properties and immobilize extensive contaminants. GGBS (granulated ground blast furnace slag)-MgO-CaO (GMCs) was used to treat Pb/Zn contaminated soil. The physical and microstructural characteristics of stabilized/solidified contaminated soil were investigated in this study. Microstructural analysis showed that the main hydration products of GMC treated contaminated soil were C–S–H and hydrotalcite like gels (Ht), which dominated the physical strength of S/S soil. The unconfined compressive strength (UCS) and the leachability of GMC treated contaminated soil were improved with the increase in GMC proportion (5%–15%), curing time (7 days and 28 days) and temperature (5 °C, 21 °C and 45 °C) due to the enhanced hydration. The compressive strengths of the majority mixes met the US EPA criterion (0.35 MPa). The strength of S/S soils was less affected by the increase of curing temperature after a longer curing period (28 days). According to the XRD and SEM results, both Pb and Zn in S/S contaminated soil could be immobilized by the precipitation and the adsorption on the surface of calcium silicate hydrate (C–S–H). Zn can also be incorporated into the structure of C–S–H and Ht. The addition of Pb/Zn decreased the physical strength in the order of: Pb(5000 mg/kg)>Pb(10000 mg/kg)>Zn/Pb(5000 mg/kg)>Pb(20000 mg/kg).