Study On Mechanical Properties And Durability Of Pb Contaminated Soil Solidified By Alkali Slag Composite

Recently,with the relocation and development of China's industrial enterprises,a large number of heavy metal contaminated soil sites are left in urban areas,and untreated heavy metal contaminated soil sites are used in engineering construction.Due to the change of soil physical and chemical properties,there are problems such as cracking of walls and pavements and uneven settlement of foundations in practical engineering applications.Therefore,the restoration and utilization of heavy metal contaminated sites has become a hot topic.With the energy consumption and environmental problems brought by traditional cement materials becoming more and more prominent,seeking new efficient and green curing agent materials is more in line with China's development goals.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(ALW2020YF13).In this paper,blast furnace slag and desulfurization gypsum are used as composite materials,and sodium hydroxide is used as activator to form alkali-activated slag cementitious material to solidify lead-contaminated soil.Through laboratory tests and theoretical analysis,the mechanical properties,water stability and durability of solidified soil under freeze-thaw and dry-wet cycles are studied.Based on microscopic tests,the solidification mechanism of solidified soil is analyzed.The main conclusions are as follows:(1)The results of unconfined compressive strength test show that the strength of solidified soil increases with the increase of age,and the early strength of the sample increases rapidly,and the later growth trend slows down.The strength of the sample decreases with the increase of lead content,and the weakening effect of lead ions on the strength is more obvious with the increase of lead content.With the increase of lead content,the failure strain of the sample increases and the plasticity of the sample increases.(2)The results of immersion test show that the softening coefficient of the sample increases with the increase of age,and decreases with the increase of lead content.The softening coefficient of the solidified soil is greater than 70%,indicating that the solidified soil has good water stability.(3)The results of SEM and XRD tests showed that the hydration products of curing agent adhered to each other and filled the pores,thereby increasing the strength of solidified soil.With the increase of lead content,the amorphous substance in the soil is more obvious,which is the precipitation generated by the reaction of lead ions,and lead ions are fixed in the soil in this form.(4)The results of single freeze-thaw and dry-wet cycles show that under the action of single freeze-thaw and dry-wet cycles,with the increase of cycles,cracks appear on the surface of the sample,the mass decreases,and the strength decreases.The strength regression model based on the number of freeze-thaw cycles shows that with the increase of the number of cycles,the strength decreases first quickly and then slowly,and finally tends to be stable.Based on the functional regression model analysis among compressive strength,failure strain and deformation modulus,it can be seen that the failure strain of the specimen decreases with the increase of compressive strength,the deformation modulus decreases with the increase of failure strain,and the deformation modulus increases with the increase of compressive strength.Figure[63];Table[12];reference[118]...