Experimental Study On Mechanical Properties Of Waste Incineration Fly Ash Used As Roadbed Filler

Waste fly ash is the fine particulate matter produced by the incineration of domestic waste,and is identified as hazardous waste because it contains a large amount of heavy metals,dioxins and soluble salts.It can be used as roadbed filler after harmless treatment,which can save huge disposal costs and reduce environmental hazards.The paper experimentally analyzes the physical,mechanical,chemical and mineralogical properties of waste fly ash,theoretically analyzes the strength formation mechanism of its use as roadbed filler,and obtains the optimal roasting treatment method through experiments.The mechanical and engineering properties of roasted waste fly ash used as roadbed filler were studied in combination with theory and experiment,and were verified by mineral composition and microstructural analysis.The main conclusions are:（1）Waste fly ash has light specific gravity,low moisture content,fine particles,good plasticity,more CaO,SiO₂and Al₂O₃content,and higher calcite and anhydrite components,which are the material basis for its reprocessing as a roadbed filler;（2）The preferred reprocessing method of waste fly ash is internal combustion roasting.80%waste fly ash is mixed with 20%pulverized coal crushed to less than 4mm and water is added to form an internal combustion billet.The leaching concentration of heavy metals in the fly ash of roasting waste is far below the standard limit,and the removal rate of dioxin-like organics and chloride salts is over 99.9%.The increased CaO and CaSO₄components and the generated Ca₂SiO₄are the strength sources of its use as a roadbed filler;（3）The load-bearing ratio of roasting waste fly ash is 6.14%,which can be used as highway embankment and road bed filler alone.The 7d uniaxial compressive strength of the specimen mixed with 4～6%cement reaches 0.53～0.71MPa,and the 14d uniaxial compressive strength of the specimen mixed with 8～10%lime reaches 0.56～0.63MPa,both of which can be used as highway subgrade base fillers;（4）Under the freeze-thaw cycle and dry-wet cycle,when the cement content is 6%,the compaction degree is≥95%,or the lime content is 10%,and the compaction degree is≥97%,the mechanical properties of the roasting waste fly ash roadbed filler better.In the engineering design,the mechanical index after 7 freeze-thaw cycles and dry-wet cycles should be used as design values;（5）When roasting fly ash is used as roadbed filler,a series of hydration reactions and pozzolanic reactions occur,resulting in cementitious substances such as Ca（OH）₂,CaSO₄2H₂O,C-S-H,CaAl₂Si₂O₈4H₂O,which increase the strength and stability of the roadbed.The waste fly ash is roasted and used as a roadbed filler,which has both economic,environmental and safety benefits,and provides a theoretical basis and technical support for the treatment and utilization of waste fly ash and highway subgrade construction.The paper has 55 figures,16 tables,and 90 references.