| The effective resource utilization methods for solid wastes such as phosphogypsum,mineral slag,and carbide slag are lacking,becoming important constraints for the upgrading and transformation of related industries.In this paper,phosphogypsum,mineral slag,and carbide slag were studied to analyze their high-value utilization pathways in preparing solidification agents and their feasibility and economic benefits in solidifying silt soils.A series of experiments were conducted to evaluate the physicochemical characteristics and mechanical properties of the composite solidification agent made up of the three components at different ratios,and the optimal ratio of the waste solidification agent was obtained.The mechanical properties of solidified silt soil were evaluated by combining indoor compaction tests with theoretical analysis.A series of tests were also conducted to evaluate the durability of the solidified soil under water exposure conditions.The environmental effects and economic feasibility of the solidified soil were explored using a combination of indoor experiments and theoretical analysis.The components,structure,and chemical reactions of the solidification agent were studied using a series of microscopic characterization methods such as SEM,XRD,and FTIR to investigate its solidification mechanism.Based on the research results,a new method for preparing and optimizing solid waste-based solidification agents was proposed,and theoretical references for the solidification of weak soils were provided.This study provides feasibility and technical support for the utilization of waste resources,promotes the recycling of solid waste,reduces resource waste,and contributes to sustainable development.The results are as follows:(1)The 28-day strength of the solidified agent increased significantly,with a 28-day unconfined compressive strength of 12.35 MPa and a flexural strength of 8.6 MPa for the(5)PKD group,which were significantly higher than those of the cement control group.Within a certain range,with a decrease in the amount of phosphogypsum and an increase in the amount of mineral powder and calcium carbide slag,the setting time was shortened.The p H of the(5)PKD group was the lowest at 28 days,indicating a higher degree of hydration of the system.(2)The maximum dry density increased first and then decreased with an increase in the content of solidified agent,while the optimum moisture content showed a decreasingincreasing-decreasing trend.The unconfined compressive strength test revealed that the strength of the solidified soil with a 15% dosage of the solidification agent reached 1.6 MPa at28 days,which was significantly higher than that of the lime and fly ash control groups with the same dosage.The moisture content and p H of the specimens both decreased with the increase in curing age.(3)The water stability coefficient of the solidified soil with a 15% dosage of the solidification agent was 62.58%,while those of the lime and fly ash control groups were almost0%,and the water stability coefficient increased with the increase in curing age.The strength of the solidified soil decreased first,then slightly increased,and then decreased again after undergoing dry-wet cycling tests.After 5 cycles of dry-wet cycling,the strength retention rate of the solidified soil with a 15% dosage was 79.37%,while that of the lime soil was 60%,and the fly ash soil collapsed after the first cycle of dry-wet cycling.After 10 cycles of freeze-thaw cycling,the strength of the solidified soil with a 15% dosage increased.This indicates that the solidified soil has good water stability and resistance to dry-wet cycling and freeze-thaw cycling.(4)The leaching concentration of phosphorus and fluorine in the solidified soil decreased with the increase in curing time.The PKD20 group had the highest leaching concentration of phosphorus at 7 days,which was 0.079 ug/m L,while the PKD5 group had the highest leaching concentration of fluorine at 7 days,which was 4.451×10-2 ug/m L.The leaching concentration of phosphorus and fluorine both met the national standard limit values.The formation of hydrated products,such as calcium aluminate and hydrated calcium silicate,in the solidified soil was observed by means of XRD,SEM,and TGA.Market research and economic analysis revealed that the use of solid waste solidified agents to treat soil not only effectively reduces treatment costs but also improves treatment efficiency and resource conservation.The research results of this study provide theoretical references and guidance for the optimization and preparation of solid waste-based solidification agents and the solidification of soft soils.Additionally,this study holds significant practical implications for the recycling of solid waste,reducing the cost of waste treatment,and achieving the effective utilization of resources. |
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