Mechanical behavior of copper-contaminated soil solidified/stabilized with carbide slag and metakaolin
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ORIGINAL ARTICLE
Mechanical behavior of copper‑contaminated soil solidified/stabilized with carbide slag and metakaolin Yin‑Juan Sun1 · Jing Ma2 · Yong‑Gui Chen2 · Bang‑Hong Tan3 · Wei‑Jia Cheng4 Received: 3 May 2020 / Accepted: 4 September 2020 / Published online: 15 September 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Different doses of carbide slag and metakaolin are used to solidify/stabilize copper-contaminated soil in accordance with its degree of contamination. This paper presents some experimental findings on the physical and chemical properties of the treated soil, including unconfined compressive strength, stress–strain state and pH, explained by series chemical and mineralogical reactions in the solidified/stabilized soil. Results showed that the unconfined compressive strength decreases and the failure strain increases with the copper ion concentration in the soil increasing. Additionally, the failure mode of the soil gradually changed from fragile failure to plastic failure. Increasing the amount of carbide slag favored improvements in unconfined compressive strength, yet decreased the failure strain. Furthermore, the pH of the soil decreased from 8.22 to 4.36 with the initial concentration of heavy metal in the contaminated soil increasing. High concentrations of C u2+ react − 2– with OH in pore solutions to form complexes like [Cu(OH)4] to decrease alkalinity in the soil. Additionally, under certain conditions, the reaction of carboxyl (–OH) and hydrated groups (–OH2) with C u2+ release H +, which will also reduce the pH value in the soil. However, when the carbide slag content increased from 5 to 15%, the pH increased significantly, up to 10.5, demonstrating the beneficial effect of the industrial waste carbide slag in solidifying/stabilizing the copper-contaminated soil. Keywords Copper · Contaminated soil · Stabilization/solidification · Carbide slag · Stress–strain characteristics
Introduction * Yong‑Gui Chen [email protected] * Wei‑Jia Cheng [email protected] Yin‑Juan Sun [email protected] Jing Ma [email protected] Bang‑Hong Tan [email protected] 1
Tunnel and Underground Engineering Research Center of Jiangsu Province, Nanjing 210041, People’s Republic of China
2
Department of Geotechnical Engineering, Tongji University, Shanghai 200092, People’s Republic of China
3
Nanning Highway Operation Limited Company, Guangxi Communication Investment Group Co. Ltd., Nanning 530022, China
4
Xuhui District Municipal Construction and Management Commission, Shanghai 200030, People’s Republic of China
The content of copper in soil has exceeded the capacity of soils to bind this element in non-bioavailable forms in many locations worldwide. This has taken place as an effect of bulk copper mining, the excessive use of copper fungicides in agriculture, urban sludge composting, and the inadequate processing of copper-containing garbage. This in turn has contributed to global heavy-metal pollution (Wang et al. 2018a, b). According to the first nation
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