Development And Heavy Metal Ions Solidification Mechanism Study Of UHPC Including Municiple Solid Waste Incineration Fly Ash

The development of green recycling technology to solve the pollution problems caused by the landfill and disposal of municipal solid waste incineration fly ash（MSWIFA）is an important guarantee for sustainable development of economic society.This paper takes a kind of MSWIFA from Nanjing Environmental Renewable Energy Co.,Ltd.as the raw material,and proposes a method of recycling MSWIFA by using ultra-high performance concrete（UHPC）as the packaging material.In this study,the leaching behavior of heavy metal ions in the MSWIFA-UHPC component was systematically evaluated.Then the adsorption of heavy metal ions by C-S-H gel（the main hydration product of UHPC）was investigated by molecular dynamics,which revealed the degradation mechanism of heavy metal ion leaching on the mechanical properties of C-S-H gel.Based on this,the hydration process,microstructure evolution and macroscopic performance development of MSWIFA-based UHPC were systematically characterized,which provided theoretical basis and technical support for the safe,efficient and high-value utilization of MSWIFA.The main research contents and results of this paper are as follows:（1）The leaching concentrations of Pb²⁺,Zn²⁺and Cu²⁺in the MSWIFA-based UHPC mixture are 1.22,23.45 and 6.18 mg/L,respectively,which are far lower than the requirements of Chinese standard（GB5085.3-2007）,indicating that the use of UHPC can effectively consolidate heavy metal ions in MSWIFA.Molecular simulation results show that C-S-H gel,the main hydration product of UHPC,solidifies heavy metal ion through ion exchange,and C-S-H gel possesses the strongest chemisorption effect on Pb²⁺.（2）The addition of MSWIFA inhibits the hydration process of the UHPC system,deteriorates its pore structure,and reduces the compressive strength of the samples.However,the compressive strength of UHPC mixed with 12.5%MSWIFA still exceeds120 MPa,which meets the mechanical performance requirements of UHPC structural applications.In addition,the addition of MSWIFA reduces the workability of UHPC due to its high surface area and porous structure.（3）Molecular dynamics simulation studies show that the interaction between Pb²⁺,Zn²⁺and Cu²⁺with the silicon chain is significantly weaker than that with Ca²⁺.The introduction of heavy metal ions significantly reduces the cohesion between the C-S-H layers,which is another important reason for the deterioration of the mechanical properties of UHPC.In this paper,UHPC is used to achieve safe solidification of MSWIFA.Molecular dynamics is applied to reveal the solidification mechanism of cement-based materials on heavy metal ions and the degradation mechanism of heavy metal ions to the performance of main hydration products（C-S-H gel）.The macroscopic performance characterization results prove that MSWIFA-based UHPC exhibits good workability,ultra-high strength and excellent durability,which indicates the prospect of large-scale structural application.Therefore,this study provides a theoretical basis and technical support for the recycling of MSWIFA,and also provides ideas for the recycling of other industrial solid wastes or other harmful materials with high heavy metal content.