| Since the National Twelfth Five-Year Plan proposed to develop urban rail transit,metro rail transit has rapidly started and developed in large and medium-sized cities in China.With the rapid development of rail transit,various traffic noise pollution problems caused by the operation of rail transit have come to the fore.This kind of noise pollution not only affects people's normal work,study and life,but also harms human health.Therefore,it is particularly important to prevent and control the noise generated by rail transit.At present,the noise absorption and noise reduction of laying subway sound-absorbing panels is a very popular subject and direction,but there are less sound-absorbing and noise-reducing materials that are suitable for special underground orbital environments and have good sound-absorbing performance.The ceramsite concrete subway sound-absorbing panels made of raw materials for pellets have recently emerged and developed in the practical engineering of subway tracks because of their environmental protection and sound absorption properties.Application practice shows: Although the ceramsite concrete material has good sound absorption performance,it is not ideal for low-frequency sound absorption(200 Hz ? 400 Hz).Therefore,further optimization of the noise reduction function of the ceramsite concrete track slab is the purpose of this paper.According to the principle of sound absorption of porous materials and the method of preparing porous sound-absorbing materials by the foaming method,heat treatment of fly ash non-fired ceramsite was performed to prepare porous ceram sound-absorbing raw materials with certain porosity and pore structure.A ceramsite concrete track sound-absorbing board was developed to improve the absorption of low-frequency noise in the subway environment.This article analyzes the physical and chemical properties of the fly ash non-sintering porous ceramsite raw material and the foaming agent,as well as the thermal analysis,and determines various factors affecting the heat treatment effect of the porous ceramsite;Combined with scanning electron microscope(SEM)observation of the internal structure of the fly ash non-sintering porous ceramsite(including pore size and distribution range,pore morphology features,etc.),to explore the heating rate of heat treatment,curing time before heat treatment and blowing agent The influence of content on the apparent porosity and pore structure of ceramsite;Through the sound absorption performance test of the standing wave tube,it is confirmed that the apparent porosity and pore structure of the material can be improved by the foaming method and the low temperature heat treatment,which can effectively improve the sound absorption performance of the material to low frequency sounds.In order to complete the above research content,this article mainly carried out the following research work:(1)The physical and chemical properties of each raw material used to prepare ceramsite and its impact on the ball formation process were analyzed.Combined with the analysis result of a simultaneous thermal analyzer with a 0.5% foaming agent dosage and a curing time of 0h,the powder was determined.The temperature rising range of the heat treatment mechanism of the fly ash-free sintering ceramsite(defined as 20°C?300°C)clearly defines the rate of temperature increase,the amount of blowing agent added,and the curing time on the porosity,pore structure,physical properties and sound absorption performance of the ceramsite.The main controlling factors of the influence;Based on this,70 sets of experiments were designed to carry out experimental research on improving the physical and acoustic properties of the fly ash-free sintered porous ceramic granules before and after the process.The macroscopic test results and the microscopic test characterization were mutually confirmed,and the heat treatment mechanism and foaming were studied.Effect of Dosage on Porosity,Pore Structure,Physical Properties and Sound Absorption Properties of Fly Ash-Free Sintered Porous CERA.(2)The method for testing the porosity of porous materials was designed to measure and calculate the porosity of ceramsite.The results of the analysis of the porosity and morphology of ceramsite with the different heat treatment mechanisms and the amount of blowing agent were compared with those of SEM.The relationship between porosity and microstructure,foaming agent content,heat treatment temperature rising rate and curing time,combined with vapor pressure principle and thermal stress mechanism caused by temperature gradient in heat treatment process,are analyzed to investigate the causes of changes in porosity and pore structure.The controllability of the microscopic pore structure of the ceramsite was realized,providing theoretical support and experimental data for the later design and preparation of porous ceramsite.(3)According to "Light-gathering materials and test methods-Part 2: Test methods for light-weight aggregates"(GB17431.2-2010),the physical properties of cylinders such as cylinder compressive strength,1h water absorption and bulk density were analyzed and tested;Based on the experimental phenomena and results data,the variation rules of the physical properties of ceramic particles under different heat treatment and foaming agent dosages were summed up,and compared with actual measured ceramic porosity and pore structure,combining physical properties and objects.The related theory of the internal structure analyzes the reasons for the change of the physical properties of the ceramsite and whether the test meets the specifications and the requirements for use.(4)Based on the sound absorption performance test instrument of standing wave tube,the sound absorption performance of different ceramsites with different heat treatment mechanisms and foaming agents was analyzed.On the basis of experimentally measured data,the effects of various heat treatment mechanisms and blowing agent content on the sound absorption properties of ceramsite were summarized.(5)Summarizing the research results and combining the research conditions,this paper puts forward the theoretical and experimental research areas that need to be further improved in the later stage of this paper,and puts forward the ideas and plans for the later research work. |
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