Preparation And Properties Of Closed-pore Foamed Ceramics Based On Granite Waste

Granite waste is the main aluminum-silicon solid waste emitted by granite stone processing industry.The comprehensive utilization of granite waste is not only beneficial to ecological protection,but also reduces the development of natural resources.High-temperature foamed ceramic partition board based on solid waste is a new type of wall material and has a broad application prospect in the field of prefabricated construction.In this thesis,foamed ceramics,with a closed porosity of more than 75%,was prepared under the principle of high-temperature foaming,with granite waste as the main raw material and Si C as high-temperature foaming agent.The experimental scheme was optimized through orthogonal experiments.On this basis,the influence of process conditions(preparation process and heat treatment process)and green body compositions(Si C particle size and dosage,granite waste dosage)on the composition,structure and properties of foamed ceramics was further studied.The main conclusions obtained are as follows:(1)Through comprehensive analysis of the orthogonal test results,the optimized experimental scheme was obtained:1200℃of firing temperature,30 min of holding time,0.8 wt%of Si C content and 90 wt%of granite waste.After firing,foamed ceramics was obtained with apparent density of 0.48 g/cm3,water absorption of 1.74%,cold crushing strength of 7.2 MPa,and thermal conductivity of 0.12 W/(m·K).(2)The four preparation processes of foamed ceramics(mud firing,powder firing,machine pressure firing and granulation firing)had little effect on apparent density and true porosity,but granulation firing preparation processes obviously improved closed porosity,reduced water absorption,and improved cold crushing strength of the foamed ceramics.(3)Increasing heating rate from 1℃/min to 5℃/min had little effect on the maximum closed porosity of foamed ceramics,but as the heating rate increases,the pore size of the foamed ceramic decreased and the firing temperature corresponding to the maximum closed porosity increased from 1180℃to 1220℃.Increasing firing temperature and prolonging holding time both led to a significant increase in the pore size of foamed ceramics,and thermal conductivity and cold crushing strength showed a downward trend.With the increase of firing temperature and the extension of holding time,closed porosity of foamed ceramics increased first and then decreased,and water absorption decreased first and then increased.When firing temperature was 1220℃and holding time was 30 min,the maximum closed porosity was 76.91%;when firing temperature was 1200℃and holding time was 30 min,the minimum water absorption rate was 1.74%.(4)Reducing Si C particle size was beneficial to increase the closed porosity of foamed ceramics,but it led to a decrease in apparent density and cold crushing strength.As particle size of Si C decreases,the pore size of the foamed ceramic increased,and the number of small holes on the pore wall gradually increased,resulting in an increase in water absorption.Si C content increased from 0 to 1.2 wt%,the pore size of foamed ceramics gradually increased,and the number of small holes on the pore wall increased,also resulting in an increase in water absorption.When Si C content was less than 1.0wt%,increasing Si C content was beneficial to improve closed porosity of foamed ceramics.When Si C content was 1.0 wt%,closed porosity was 78.68%at the maximum,and apparent density was 0.44 g/cm~3,with 5.35 MPa of cold crushing strength.As granite waste content increases,closed porosity of foamed ceramic increased first and then decreased,and water absorption rate and thermal conductivity decreased first and then increased.Granite waste content in the range of 85～95 wt%had little effect on the performance of foamed ceramics.Closed porosity was slightly reduced in the range of75.6～77.1%with water absorption less than 6%,and the maximum thermal conductivity was 0.17 W/(m·K).