Considerations on sound absorption coefficient of sustainable concrete with different waste replacements

In the context of an urban environment assaulted by noise from different sources, the possibility of using composite materials made of concrete and various materials considered as waste was investigated, for the purpose of using them in acoustic barriers. Five different types of sustainable concrete have been developed, incorporating polystyrene granules, polyethylene terephthalate granules, corn cob granules, shredded sunflower stalk and balls made of sheep wool. Two different thicknesses were adopted, of 40 mm and 80 mm. The influence of the material's thickness was investigated. For these materials, the acoustic absorption coefficient was determined, using Feng's modified procedure of the ISO 10534:1998 standard. The sound absorption coefficient's meaning suffers changes and its measured value can be considered the real one, smaller than the usual reported standard values. Each of the sustainable concrete has sound absorption coefficients higher than those of the conventional concrete. The results highlighted that these types of materials represent a sustainable solution for both waste and noise problems of our cities.