Study On The Preparation And Fire Prevention Characteristics Of Industrial Solid Waste Based Composite Slurry Foam Materials

Mine air leakage is one of the major reasons for coal spontaneous combustion.Coal spontaneous combustion disasters often bring some bad effects,such as economic losses and casualties,gas explosions and other accidents.Effective blocking of air leakage channels is the key to preventing coal spontaneous combustion.The existing inorganic plugging and filling materials mainly include cement-based slurry,water glass gel,etc.,which play a significance role in the prevention and control of coal spontaneous combustion.But they are offen exhibit brittle failure when applied,and there are problems such as low solid waste utilization rate,large cement consumption and high cost.Therefore,the development of environmental-friendly,safe and efficient plugging and filling materials is the development trend of fire prevention technology.Based on that,this thesis proposed a composite slurry foam material and plugging technology with industrial solid waste as the base material based on the concept of promoting green cementitious materials and helping to achieve the"dual carbon"goal,and obtaining the following research results:The formation process and solidification mechanism of industrial solid waste-based composite foamed slurry were studied.A composite foamed slurry with solid waste,cement and water-based foam as the main raw materials was invented.Highly stable water-based foam is the basis for the formation of composite foamed slurry.Based on the synergistic effect between surfactant and organic polymer molecules,this thesis developed a foaming agent that was suitable for industrial solid waste,cement and other cementitious slurries,which enhanced the strength and viscoelasticity of the liquid film of bubble in the slurry,and slowed down the foam drainage rate.When the water-based foam was mixed with the composite slurry containing solid waste and cement,the bubbles and the gel particles were fully mixed to produce random collision and adsorption.And the hydrophilic groups such as-COO-and-OH in the polymer molecule underwent complexation reaction with basic salt ions and solvated with water molecules,so that the gelled particles were adsorbed on the bubble liquid film,further forming composite foamed slurry consisting of a stable_—cell_—stru_—cture.With the time went by,the multi-component gelling components,C₄A₃S-C₂S-CSH₂-Ca CO₃-H₂O in the foam slurry occurred a hydration reaction.Products such as high-sulfur ettringite,aluminum glue,hydrated calcium silicate gel and calcium hydroxide were formed on the surface of the cells,which gradually solidified and filled the cell skeleton structure.Finally,the industrial solid waste-based composite foamed slurry was prepared.The influence of the composition ratio on the main parameters of the industrial solid waste-based composite foamed slurry was studied.The reasonable ratio range of the industrial solid-waste-based composite foamed slurry was determined.The results showed that when anionic surfactant and zwitterionic surfactant were compounded in a mass ratio of 6:4,and polymer with ratio of 4‰was added,the water-based foams with high stability could be prepared.The effects of three solid wastes including fly ash,silica fume and slag on the fluidity,expansion ratio,compressive strength and microstructure of the composite foamed slurry were studied respectively,and slag was selected as the raw material of the composite foamed slurry.The pozzolanic activity of slag was improved by a combination of physical milling and chemical excitation.The effects of the fineness and dosage of slag,and the dosage of activator on the strength of composite foamed slurry were investigated.The reasonable ratio range of the composite foamed slurry was determined:the slag content was 55%～65%of the cementitious material,the sulfoaluminate cement was 45%～35%;the foam content was 2 times that of the composite slurry,the water-binder ratio was 0.45～0.5,and the activator content was 2%～4%.The composite foamed slurry prepared at this time has the best comprehensive performance.After curing,the dry density of composite foamed slurry is 410kg/m³～450kg/m³,the compressive strength is 0.45MPa～0.55MPa,and the content of solid waste reaches up to 65%,realizing the efficient utilization of industrial solid waste.The flow diffusion and bonding reinforcement characteristics of the industrial solid waste-based composite foamed slurry were studied.The rheological model of the composite foamed slurry was constructed.Moreover,the bonding mechanism of the contact interface between the composite foamed slurry and the coal was clarified.The steady-state rheological law of the composite foamed slurry with different water-binder ratio and foam content was explored,and the results showed that the composite foamed slurry exhibited obvious shear thinning behavior.It was found that the Herschel-Bulkely equation could describe the rheological behavior of the foamed slurry fluid well（fitting coefficient>0.99）by fitting the shear stress-shear rate curve of the composite foamed slurry,which indicated that the composite foamed slurry is a kind of pseudoplastic fluid with yield stress.Based on the rheological constitutive model of the composite foamed slurry,the diffusion equation of the foamed slurry in the crack channel was theoretically deduced.The results show that the rheological index,viscosity and crack width are the key factors affecting its diffusion performance.The surface morphology,functional groups and micro-component characteristics of the contact interface of the composite foamed slurry-coal were studied.It was found that the active groups on the foamed slurry and coal molecules occurred chemical bonding and physical coating between the interface.A composite foamed slurry-coal interfacial bonding model composed of weak effect layer,enrichment layer,contact layer and etching permeable layer was established to provide theoretical guidance for the field application of composite foamed slurry in underground air leakage areas.The effect of plugging air leakage and the fire-extinguishing characteristics of the composite foamed slurry were studied,and the effectiveness of the plugging and filling technology was verified in the field test.The study showed that the coagulation and forming time of the composite foamed slurry is controllable and adjustable from15 to 30 minutes,which could meet the needs of plugging construction in underground air leakage areas.When the plugging thickness of the composite foamed slurry exceeded 60mm,it exhibited excellent heat resistance stability and oxygen barrier effects.By testing the seepage process of the composite foamed slurry in the stacked coal block,it was found that it could rapidly diffuse upward and accumulate,cool the high-temperature coal in the quenching model,and the coal temperature drops from 290°to 39.5°within 30 minutes.After being placed for 3 days,the coal block was completely wrapped and bonded to form a whole,showing the excellent fire extinguishing,cooling,bonding,and reinforcement effects of the composite foamed slurry.In addition,the on-site construction process for filling and plugging the leakage area with composite slurry foam was designed.Taking the caving of air leakage from the roof cracks in the caving area as an example,the composite slurry bubble was used to effectively block the air leakage channel to prevent the air flow from staying in the high caving area,and simultaneously,the loose coal was bonded and strengthened,in order to realize the control of the hidden coal spontaneous combustion in the high caving area.This thesis contains 135 figures,54 tables and 205 references.