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| Study on the strength and leaching characteristics of solidified/stabilized lead，zinc and cadmium contaminated soil with red mud-based curing agent |
| GUO Mingshuai，PAN Hao，WANG Fei |
| (Institute of Geotechnical Engineering，Southeast University，Nanjing，Jiangsu 210096，China) |
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Abstract Red mud-phosphogypsum-cement(RPPC)，red mud-phosphogypsum-quick lime(RPCA) and ordinary cement(PC) were used to solidify/stabilize the artificially prepared lead，zinc，and cadmium contaminated soil. Then the ratio of red mud-based curing agent was optimized. After the samples were cured for 7 days and 28 days respectively，unconfined compressive strength，toxic leaching test and pH gradient test were carried out. The research results show that with the increase of curing agent content and curing age，the unconfined compressive strength of the samples cured with red mud-based curing agents gradually increases. The difference between the strengths gradually increases. The pH of the leaching solution of the samples cured by the three curing agents are in the range of 7–9. After 28 d curing age，the red mud-based curing agents with 15% content have good strength and curing effect. In comparison，RPPC has better solidifying/stabilizing effect than RPCA. And RPPC has higher unconfined compressive strength and lower heavy metal leaching concentration. The pH gradient test results show that the leaching concentration of heavy metals in RPPC solidified samples was the lowest when pH = 8. Under different pH values of the extractant，the leaching concentration still meets the trend of increasing with the increase of the content.
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2021, Vol. 40 
