| With the rapid industrialization of gypsum in China,the problem of heavy metal soil pollution is becoming more and more serious.How to repair the heavy metal contaminated sites and how to dispose of the remediated soil has become an urgent social problem.At present,solidification stabilization method is one of the most widely used methods to treat heavy metal contaminated soils.It is of great significance to study new solidifying agents which can effectively and economically remediate heavy metal contaminated soils and the resource utilization of solidified soils.Based on the mechanism of inorganic materials solidifying heavy metal contaminated soil and the concept of waste treatment,blast furnace slag,quicklime and phosphogypsum were selected as composite solidifying agent of industrial waste residue.The solidifying effect and the feasibility of solidified soil as roadbed filler were studied.The main research results of this paper are as follows:(1)The strength and leaching characteristics of solidified soil were analyzed,and the optimum mix ratio of industrial waste composite solidifying agent was studied by means of orthogonal experimental design.The results showed that the content of quicklime had the greatest influence on the 7d strength and leaching characteristics of solidified soil,and the change of blast furnace slag content contributed significantly to the improvement of the later solidification effect.The relationship between the content of mixed solidifying agent and the unconfined compressive strength of solidified soil and the concentration of leachate Pb2+ was modeled.Based on the multi-index comprehensive scoring method,the optimum mixing ratio of solidified lead contaminated soil with industrial waste slag was selected as 9%,5% and 3.5% of blast furnace slag,quicklime and phosphogypsum,respectively.(2)The results show that the resistivity of solidified lead contaminated soil increases with the increase of curing age and decreases with the increase of initial lead ion concentration,and there is an exponential function relationship between the resistivity of solidified lead contaminated soil and the initial lead ion concentration and curing age of solidified soil.The ratio is positively correlated with the unconfined compressive strength and negatively correlated with the concentration of lead ion in leaching solution.The solidification effect of heavy metal contaminated soil can be evaluated by measuring the resistivity of solidified soil.(3)The road performance of industrial waste solidified soil,cement solidified soil and non-solidified contaminated soil were studied.The results showed that the CBR and compressive resilience modulus of industrial waste solidified soil and cement solidified soil could meet the specifications,and the non-solidified contaminated soil could not be used as roadbed filler for high-grade highway;the effects of dry-wet cycling and freezethaw cycling on solidified soil and non-solidified soil were studied.The strength and leaching properties of the stabilized soil with industrial waste residue of 1000mg/kg and 5000mg/kg initial lead ion concentration are affected to a certain extent.The leaching solution concentration of solidified soil with industrial waste residue of 1000mg/kg initial lead ion concentration is less than 5 mg/L after 10 dry-wet cycles and freeze-thaw cycles,but the leaching solution of solidified soil with industrial waste residue of 10000 mg/kg initial lead ion concentration is subjected to 10 dry-wet cycles and freeze-thaw cycles.The concentration of lead ions exceeded the limit of the specification. |
