Mechanical Behavior And Micro Mechanism Of Red Mud-Municipal Solid Waste Incinerator Bottom Ash Based Building Materials

Red mud and municipal solid waste incineration bottom ash(referred to as bottom ash in the text)are typical solid wastes that have caused serious harm to the natural environment and human society.If it can be reasonably used,the environmental problems will be improved.Taking advantage of the complementary chemical components of red mud and bottom ash and the difference in particle size,porous lightweight aggregate ceramsites are prepared in a more convenient and energy-saving way,which has the characteristics of higher crushing strength and lower water absorption,and its typical physical properties meet the requirements of relevant regulations.Using the high alkalinity of red mud and the potential activities of the two materials,a controllable low-strength material(referred to as low-strength material in the text)was prepared,which has the potential to be used in backfilling projects such as pipe trenches and roadbeds in larger spaces.In order to reveal the evolution mechanism of the characteristics of red mud-bottom ash-based ceramsite prepared by high-temperature sintering,explore the types of red mud,the ratio of raw materials and the optimal choice of thermal system when preparing lightweight aggregate ceramsite.The thesis uses a combination of experimental exploration and theoretical analysis to explore the typical physical properties such as crushing strength,water absorption,pore characteristics and density.XRD and thermogravimetric analysis were used to reveal the evolutionary law of physical properties of ceramsite in different conditions.In order to explore the thermal activation conditions of red mud,bottom ash and the optimal ratio of raw materials under the prepared red mud-slag-Ca(OH)2 system,the modified red mud and bottom ash pozzolan activity are evaluated firstly,and then the physical properties of low-strength materials under different preparation conditions are explored.XRD,FT-IR and thermogravimetric analysis are used to reveal the mechanism and property change laws of low-strength materials.The main research results are as follows:(1)The optimal red mud type and preparation process for the preparation of porous lightweight aggregate ceramsite and low-strength materials are proposed.It is found that the ceramsite with high calcium content red mud: slag is 1:1,and the calcination temperature is1070 ℃ has the best effect The results show that the thermal activation temperature of red mud and slag is 800 ℃ and 400 ℃ respectively.(2)The relationship between the ratio of raw materials and the physical properties of ceramsite was clarified.It is found that the calcination temperature of ceramsite is positively correlated with the content of red mud.Under the same calcination temperature,the density,porosity and crushing strength of ceramsite decrease with the increase of red mud content except A1.The water absorption is on the rise,and the p H value of ceramsite decreases obviously.(3)It is found that the physical and chemical properties of red mud slag ceramsite vary with calcination temperature.The calcination temperature of ceramsite changes slightly with the proportion of raw materials.With the increase of calcination temperature,the crushing strength of ceramsite first increases and then decreases,the porosity and the proportion of macropores increase,while the water absorption and p H decrease.After heating,the mass transfer of ceramsite is more complete,and the generated glassy phase fills the interior of ceramsite,wrapping the gas and raw material particles generated at high temperature to form dense spheres.(4)The relationship between the change process of strength and microstructure of low-strength materials is clarified.The hydration reaction occurred mainly in the early stage,and the initial strength was mainly provided by aluminum containing C-S-H gel and hydrotalcite.Because of the easily carbonized of the samples,the hydration products of all samples after 28 d are less than 3d,and the main reason for maintaining the strength in the later stage is the calcite generated by carbonization of hydration products.