| Recently,with the development of industrial enterprises in China,a large number of heavy metal pollutants invade the soil,which is harmful to the surrounding environment,destroying the soil structure,and also posing a threat to human health.Therefore,the remediation of heavy metal contaminated soil has become an urgent problem.Moreover,there are many disadvantages of traditional soil-treatment materials like cement,such as high energy consumption and high carbon emission,therefore,it is significant to explore more environmentally friendly efficient curing agent to deal with the contaminated soil for the goal of China's green development.This study is funded by research foundation of the Institute of Environment friendly Materials and Occupational Health of Anhui University of Science and Technology,Wuhu(ALW2020YF02),and the study introduces a novel environmentally friendly composite,formed by sodium hydroxide(used as an activator),desulfurized gypsum and steel slag(S-GS).The main objective of this study is to evaluate the potential use of S-GS for solidifying the lead and cadmium contaminated clay under the condition of carbonation curing.Besides,the samples's mechanical properties and mechanism are investigated according to the macro test,micro test and theoretical analysis.The main research results are as follows:(1)The tests of the mechanical properties of S-GS solidified clay show that when the initial moisture content at 0.5 times liquid limit,desulphurization gypsum content at 8%and sodium hydroxide content at 2%,the solidified clay carry a good mechanical properties.In addition,microscopic tests show that the formation of carbonation products such as calcium carbonate is the main reason for the significant enhancement of the strength of the clay as well as the densification of the microscopic pore morphology.(2)The tests of the mechanical properties of S-GS solidified lead and cadmium contaminated clay and the toxicity leaching test show that the carbonation curing can effectively improve the strength of the contaminated soil,and also effectively reduce the toxic leaching amount of contaminated soil.In addition,the micro analysis shows that with the increasing carbonization time,the strength of contaminated soil increases greatly,while the leaching concentration of heavy metals decreases,which is mainly due to the formation of carbonate or basic carbonate precipitation of the heavy mental in the process of carbonization,and the heavy menta is stablized in the soil through adsorption function and the packing effects of cementitious substances.(3)The test of the long-term strength of S-GS solidified lead and cadmium contaminated clay shows that the strength of solidified soil samples at different carbonation curing time increases in the form of power function with the increase of standing time.Through the establishment of strength regression model based on standing time,besides,it can be observed that the growth rate of strength is first fast and then slow,which gradually tends to be stable.(4)The freeze-thaw cycle test of S-GS solidified lead and cadmium contaminated soil shows that the increase of freeze-thaw cycles will lead to the phenomenon of cracking,spalling,mass loss and the weaken of the strength of samples,but compared with standard curing,carbonization curing can significantly help to these problems.Moreover,when curing for a longer carbonization time,it is observed that an inapparent damage,the smaller mass loss rate and the greater strength value of samples.Therefore,carbonation curing can effectively improve the ability of the freeze-thaw cycle resistance for the S-GS solidified Pb and Cd composite contaminated clay.Figure[107];Table[12];reference[144]... |
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