Study On Preparation And Performance Of Cement-based Sound Absorption Composites

With the rapid development of modern industry, noise pollution has seriously affected people’s daily life. Sound absorbing materials, which could effectively alleviate this problem, has captured a lot attention around the globe.In this paper, sound absorbing mortar and concrete were initially prepared. Systematic studies were then carried out on the factors which could influence the performance of the cement-based sound absorbing composites. These factors included the type, size, and pre-wet degree of lightweight aggregates, and different content of entraining agent and polypropylene fibers. Sound absorption performances of these two types of samples were measured and the microstructures were then characterized by scanning electron microscope and stereomicroscope.Experimental results showed that type of lightweight aggregates could significantly affect sound absorption and mechanical properties of cement-based sound absorption composites. In terms of the fine aggregates, expanded perlite showed enhanced sound absorption performance, as its internal porosity is higher than that of vermiculite. Among all the three coarse aggregates, pumice showed the best sound absorption performance and mechanical property, especially when the size of the pumice ranged between 5 to 10 mm. Additionally, pre-wet on the lightweight coarse aggregate for 1 h in advance could improve the sound absorption and mechanical properties of concrete as well. Introduction of air entraining agent could form a large number of small, interconnected porosity into mortar and concrete, thereby improving sound absorption performance of mortar and concrete. As the content of air entraining agent gradually increased, the sound absorption coefficient increased first and then decreased, the optimum loading of entraining agent is 0.3 %. Addition of the Polypropylene fiber could form interconnected porosity inside concrete, thus improving the sound absorption performance of the concrete and mortar. The content of Polypropylene fiber could positively affect the average absorption coefficient and noise reduction coefficient of concrete. Thickness could also play an important role in the performance of cement-based composites. The sound absorption coefficient at the frequencies below 250 Hz increased with the increase of the thickness of material. The optimal thickness turned out to be 120 mm at low frequency range. Sound-absorbing properties of the material mainly depends on the effective porosity inside the material, a larger internal effective porosity could increase the acoustic reflection and friction with the hole walls, converting more sound energy into heat energy, improving the sound absorption performance.