Effect of Aggregate Size and Gradation on the Ceramsite Sound-absorbing Materials

In this paper, the effect of ceramsite aggregate size and gradation on the sound absorption and mechanical properties of the materials were studied and the relationship between material's pore structure and its sound absorption were discussed. It can be found from the results that the sound absorption and mechanical properties of the ceramsite sound-absorbing materials increase with the content of the fine ceramsite increased due to the decrease of the median pore diameter of the ceramsite sound-absorbing materials where the improvement of the sound absorption at the high frequency band is more significant suggesting that fine pores have a better sound-absorbing effect for high-frequency noise. Higher effective porosity doesn't mean better sound absorption, because materials with coarse pores have shorter internal routes for sound waves and less friction during sound waves passing through pores, which conversely decreases the material's sound absorption. Ceramsite with higher internal porosity and more uniform pore diameter distribution can produce materials with better sound absorption. Ceramsite with small volume weight and numerous internal pores has certain strength and firmness, and therefore, it has the features of light weight, erosion resistance, freezing resistance, shock resistance, as well as good thermal insulation, heat insulation, sound insulation and moist insulation, etc., which can be widely used in construction, chemical, oil and other sections[1]. In this paper, the light fine ceramsite (aggregate size <5mm) was adopted as the aggregate to prepare the porous sound-absorbing materials. Because of the interconnected pores among the aggregate, it had good sound absorbing performances[2,3]. Three kinds of ceramsite gradation were studied including 100% coarse ceramsite (aggregate size 2.5mm similar to 5.0mm), 100% fine ceramsite (aggregate size 1.0mm similar to 2.5mm) and 50% coarse ceramsite + 50% fine ceramsite, all of which had 0.3 water cement ratio, 25% cement content and 4.2g water reducing agent content, and the influence of different aggregate matching on sound absorption and mechanical properties of the materials were studied. The quantitative analysis of the pore features at the material's cross-sections was carried out through the microscopic analysis to establish the relationship between the microscopic pore condition and the macroscopic sound absorption of the materials. Moreover, the influence of the ceramsite with different pore structure on the material's sound absorption was analyzed providing theoretical basis for the design of porous sound-absorbing materials from the perspective of pore structure.