Preparation Mechanism And Performance Research Of Multiple Solid Wastes Based Porous Inorganic Polymeric Materials

The large stockpiling,low utilization rate and value-added of industrial solid wastes,serious environmental pollution,and high building energy consumption ratio have severely constrain the low-carbon,high-quality and sustainable development of China’s economy.Using industrial solid wastes in the preparation of green energy-saving building materials is one of the effective and promising approaches to realize the large-scale disposal of industrial solid wastes with cost-effectiveness,alleviate the contradiction between the steady development of China’s industry and resources and environment protection,and promote the upgrading of the industrial chain of solid waste based green building materials,and thus help to accelerate the implementation of the strategic target of"carbon neutrality".The present study has the potential to be of great importance to the harmonious development of economy,society and ecology.Based on the theory of geopolymerization,this paper takes typical industrial solid wastes such as fly ash,lithium slag,coal gangue,slag and silica fume as research objects,and takes the synergy-coupling relationship between physical and chemical behavior of industrial solid waste,performance enhancement of industrial solid wastes based alkali-activated cementitious materials,green and low-carbon preparation of industrial solid waste based novel porous inorganic polymeric materials and and its application in building energy conservation as the main research objectives.By means of a series of microscopic analysis methods such as SEM,XRD,DSC/TG,FTIR,NMR,the following aspects are emphasized and systematically studied:1)Influence of mechanical force pretreatment in ball mill on the characteristics of industrial solid wastes and the synergy-coupling relationship between the solid wastes in the process of geopolymerization;2)Effects of industrial solid wastes system,activator type and curing regime on the reaction process and comprehensive properties of alkali-activated cementitious materials;3)Property regulation and sustainability of porous inorganic polymeric materials based on in-situ foaming of alkali-activated materials;4)Influence of thermal modification condition on pore structure,product system in inter-pore matrix,comprehensive performance and high value-added application potential of porous inorganic polymeric materials.The main conclusions can be drawn as follows:（1）The fluidity and setting rate of fresh slurry decreased significantly due to high content of lithium slag.Suitable amount of silica fume and slag powder and prolonging curing time can optimize slurry characteristics,improve the density and uniformity of gel matrix as well as the compressive strength.The dissolution characteristics of the highly active components and the synergic and coupling relationships between each component affect the dissolution-polymerization process,then resulting in varying degrees of change in the macro-properties,micro-morphology,Si coordination structure and gel products system of the multi-ISWs based AAMs.（2）When Na₂O/Al₂O₃ratio is less than 0.9,the concentration of OH^-decreases,leading to the weakening of depolymerization extent of aluminosilicate minerals and density of the matrix.The Ms in the range of 0.8-0.9 is conducive to the rapid dissolution-polymerization of the active aluminosilicates,optimizing the product spatial distribution and mechanical properties.Appropriately increasing curing temperature and curing time can promote the formation of polymeric gel products and increase the development rate of compressive strength.However,the gels generated under long-term high temperature curing will adhere to the particles surface to form a dense layer,which may lead to the decrease in active surface of raw materials,change of the model of reaction kinetic,and high production energy consumption.（3）With the mix design of mass ratio of fly ash,lithium slag,silica fume,slag and coal gangue is 45:30:4:16:5（Si O₂/Al₂O₃=4.3）,activator content is 14.5%（Na₂O/Al₂O₃=1.0）,activator modulus is 0.9,pre-curing temperature is 50-60℃,pre-curing time is 3d,curing age is 7d,and liquid-solid ratio is 0.5±0.05,the initial fluidity of the obtained fresh slurry is200±5 mm,the initial setting time is 30-50 min,the final setting time is 170-190 min,and the3d and 28d compressive strength of alkali-activated material can reach 30MPa and 35 MPa,respectively.（4）The increasing of foaming agent decreases the foaming stability and uniformity of pore distribution,leading to the significantly reduction of volume density,compressive strength and thermal conductivity.Introducing high amounts of foam stabilizer is inclined to form stir bubbles,which will affect the forming stability of porous body and the formation of continuous gel network structure.Rising the foaming temperature is helpful to shorten the gas generation time,but when the temperature is higher than 30℃,the gas forming rate and slurry thickening rate will not match well,resulting in the formation of a large number of connected pores.Based on the preferred alkali-activated cementitious materials prepared by multiple industrial solid wastes and the mix design of 0.17%dosage of gas forming agent,0.2%foam stabilizer and curing temperature of 30±5℃,the porous inorganic polymeric material with bulk density of 500±20 kg/m³,compressive strength ranging from 2.5 to 3.0MPa,and thermal conductivity of 0.165±0.005 W/（m·K）can be successfully prepared.Moreover,the physical and mechanical properties of the foam can meet the relevant requirements of B05,A2.5 grade autoclaved aerated concrete in Chinese standard of GB11968.（5）Reclaimed materials generated from the preparation and testing can be recycled.However,excessive reclaimed materials reduces the active silicon-aluminum composition and affects the matching relation between the slurry thickening characteristics and foaming characteristics,which is detrimental to a better gels polymerization degree and formation of dense 3D network structure,resulting in poor comprehensive performance.In consideration of cleaner production,recycling and comprehensive performance,the mixing amount of reclaimed materials should be less than 10%in mass ratio.（6）Hydrothermal conditions at 120-180℃can promote the transformation of gels into zeolite crystals,and change the crystal-to-gel ratio,phase spatial distribution,micro-porosity and morphology of inter-pore matrix.Temperature above 600℃will cause the decomposition of minerals structure,melting and grains diffusion,resulting in the formation of nepheline phases and porous and homogeneous ceramic-like frame structure.The thermal stability of inorganic polymeric materials is closely related to the product system based on multiple solid wastes mix design,and the change of microstructure and product composition will endows the inorganic polymeric materials with various physical and chemical properties,improving its application potential in multiple industries.