Study On Performance Of A Novel Sound Barrier Based On Beneficial Use Of Solid Waste

For many years,traffic noise pollution and solid waste pollution have always been two major issues in urban development.It is urgent to solve the issure that how to control traffic noise and reduce solid waste emissions so that to improve the urban environment.Sound barriers can effectively absorb noise,block sound transmission and provide residents with a comfortable and healthy living environment.The use of solid waste resources to prepare a new type of sound barrier is of great significance for improving resource utilization and reducing solid waste emissions.Fly ash is an industrial waste discharged from power plants,and fly ash cenospheres are by-products during its combustion process.Although fly ash cenospheres have been used in several fields,such us building insulation,wastewater treatment,and lightweight fillers.The application of cenospheres in acoustic materials is still relatively infrequent.This study used white cement(the compressive strenth is 52.5 MPa)to prepare a nonmetallic sound barrier made of fly ash cenospheres,so that to provide a new choice for sound barrier design.It can provide another way to reuse fly ash cenospheres and promote the recycling of solid waste resources.Experiment and numerical simulation were used in this paper to explore the performance of this novel material applied in sound barriers to control traffic noise.The following four questions were mainly studied: 1)The reasonable mix ratio and the preparation process of the sound absorption layer and the sound insulation layer.2)The performance optimization of the sound absorption layer,sound insulation layer and composite materials made of fly ash cenosphere and white cement.3)The establishment of the COMSOL simulation model of the sound absorption/ insulation layer,as well as the simulation of the noise reduction performance varied with the configuration of sound barrier.4)The structural design and environmental impact assessment of the sound barrier system made of fly ash cenospheres.In view of the above research questions,the main conclusions are as follows:Firstly,through preliminary research on the preparation of fly ash cenospheres cement-based composite material,it is found that the mechanical properties and sound insulation properties of composite materials are mainly determined by the dense sound insulation layer.Reducing the aggregate-to-binder ratio of the sound insulation layer has a significant effect on improving its compressive strength;when the aggregate-to-binder ratio of the sound-absorbing layer material is too low or the water-to-binder ratio is too high,the cenospheres will be filled with cement slurry and the slurry tends to bleed and it also will cause other unfavorable molding effects.Secondly,through single-factor experimental research on the sound absorption layer,sound insulation layer and composite material,it is found that the molding pressure of the material has a significant impact on the acoustic and mechanical properties of the cenospheres cement-based sound absorption material,and there is an optimum scope of the shaping strength,i.e 0.2MPa ～ 0.4MPa.When the shaping strength is 0.2MPa,the optimum aggregate-binder ratio is 0.9,and when the shaping strength is 0.4MPa,the optimum aggregate-binder ratio is 1.0.The waste glassfiber content of the sound insulation layer has no obvious effect on its sound transmission loss,but it has an obvious impact on its mechanical properties.The compressive capacity the sound insulation layer is optimal when the fiber content is 45%.The thickness of the specimen influences the sound transmission loss greatly,which is similar to the ’mass law’ and when the is thickness is double,its transmission loss increases by 4 d B.When two optimum sets of sound absorption layer and sound insulation layer are combined,it is found that the shaping strength of the sound absorption layer has a significant impact on the overall strength of the composite material.The strength of the C2 is 1.57 times stronger than that of C1,but there is no obvious difference between the acoustic performance of this two group of specimens.When changing the thickness ratio of the two layers of the composite material,the ratio with best acoustical performance is 60:40.At this time,the sound insulation is the highest,reaching 38 d B.Thirdly,the software COMSOL Multiphysics was used to simulate the performance of single sound absorption/ insulation layer and the numerical calculation results was vertified by the the test results.The error values between these two set of results are 18%and 13% respectively,which proved the accuracy of the numerical simulation results.Based on these paramters,the simulation of sound barrier with 10 different configurations were conducted via COMSOL.It is found that the transmission loss of the sound barrier is mainly determined by the performance of the sound insulation layer.The larger the thickness of the sound barrier is,the better the noise reduction will be.Moreover,the composite material with thicker absorption layer can reduce the influence of the standing wave of the sound field to some extent.The sound barrier with T-shaped has the best noise reduction performance,with a weighted sound insulation of 26 d B.The transmission loss of all configurations of sound barriers reached the largest value at the 315 Hz.The new type of fly ash cenospheres cement-based sound barrier is also energysaving and environmental friendly.During the life cycle of sound barrier,the embodied carbon and embodied energy of the unit panel are 48.89 kg CO2 and 349.87 MJ,respectively.Finally,based on the optimal configuration of the sound barrier calculated by the numerical simulation,the installation structure of the fly ash cenospheres cementbased composite sound barrier system is designed,in order to provide a reference for the engineering application.