Preparation And Impact Resistance Of Municipal Solid Waste Incineration Fly Ash Based Low Carbon Composite Materials

Municipal solid waste incineration fly ash(MSWIFA)is a hazardous solid waste generated during the incineration process,requiring solidification/stabilization treatment prior to landfill disposal.With landfill capacities approaching saturation,there arises an exigent demand for the formulation of a durable,sustainable,and environmentally benign disposal modality to solve the problem of no landfill for MSWIFA.Drawing upon the basic principles of alkali-activated materials,this paper innovatively explores the resource utilization of MSWIFA through the synergistic activation of multiple salt-alkali containing solid waste and the complementary action of cementitious components.The key findings and contributions of this study are as follows:(1)Optimization of MSWIFA-based low-carbon cementitious material compositions.Taking the improvement of strength and the curing rate of harmful components as the index,the cementitious material ratio of MSWIFA-carbide slag(CS)synergistically stimulated slag-red mud(RM)was optimized by changing the relative content of the main components of each solid waste,and the strength formation mechanism and the curing mechanism of harmful components were analyzed by using microscopic means,such as XRD,FTIR,and SEM-EDS.The results showed that the RM and slag decomposed under the salt-alkali environment jointly created by CS and MSWIFA,and hydration products such as C-(A)-SH,hydrated calcium chloroaluminate(HCC),and ettringite were generated.The gel-type and crystal-type products are interspersed with each other to form a source of strength and to solidify heavy metals in the form of physical encapsulation,chemical precipitation and ion adsorption.(2)Optimization of forming process for novel cementitious materials.This study delves into the optimization of the forming process for a novel cementitious material.It systematically investigates the influence of preparation parameters such as forming pressure,curing temperature,and curing duration on the strength and microstructure of the innovative cementitious material.A quantitative and qualitative relationship is established to discern the optimal parameters for compaction and curing,elucidating the underlying mechanisms through microscopic analyses.The findings underscore a non-linear relationship between strength and forming pressure,with strength increasing initially and then declining as forming pressure escalates.The optimal forming pressure is determined to be 30 MPa,resulting in a remarkable 182% enhancement in early strength.Furthermore,the optimum curing regimen is identified as 90°C for 12 h.Prolonged curing times are observed to lead to microstructural degradation,increasing the volume of macropores and detrimentally affecting the later-stage strength development.(3)Long-term stability study of a novel cementitious material in harsh environments.This study investigates the long-term stability of a novel cementitious material under adverse conditions,including high temperature,freeze-thaw cycles,and sulfuric acid erosion.It focuses on the leaching behavior of harmful constituents and establishes a model to elucidate the relationship between the microstructural evolution,the immobilization of deleterious components,and the long-term performance of the new cementitious material in eroding environments.The results reveal that under sulfuric acid erosion,there is geopolymer gel depolymerization and dealumination.Rapid development of harmful pores during freeze-thaw cycles and the decomposition of C-A-S-H gel and HCC crystals under high-temperature conditions are identified as the primary causes of strength deterioration.After immersing the material in sulfuric acid solution for 112 d,subjecting it to 50 freezethaw cycles,and calcining at 1000°C for 15 mins,the leaching concentrations of heavy metals all comply with municipal solid waste landfill pollution control standards.This indicates that the novel cementitious material exhibits excellent heavy metal immobilization capabilities.(4)Damage model for fiber-reinforced MSWIFA-based composite materials and their impact resistance.Incorporating iron tailings sand and polypropylene fibers,fiberreinforced concrete was prepared to investigate its compressive strength and impact resistance under the influence of multiple factors.By conducting a fractal dimension analysis of cracks and fracture surfaces in post-impact concrete,a quantitative relationship between total crack area,crack skeleton,and impact cycles was established.Furthermore,an impact damage evolution equation and lifetime prediction model were formulated based on a two-parameter Weibull distribution.The results reveal that a mesh-like polypropylene fiber with a length of 12 mm and a volume fraction of 1.0% exhibits excellent impact resistance.It can withstand an initial crack initiation of up to 78 cycles and a final crack occurrence of 105 cycles,resulting in a remarkable improvement in impact resistance by136.4% and 200.0%.The research outcomes further enrich the alkali-activation theory,providing a theoretical foundation and technical support for the efficient resource utilization and largescale coordinated disposal of solid wastes such as MSWIFA,CS,and RM.This work carries significant economic,environmental,and social benefits.