Performance characterization of broad band sustainable sound absorbers made of almond skins

In order to limit the environmental impact caused by the use of non-renewable resources, a growing research interest is currently being shown in the reuse of agricultural by-products as new raw materials for green building panels. Moreover, the European directives impose the goal of sustainability supporting the investigation of passive solutions for the reduction of energy consumption. Thus, the promotion of innovative building materials for the enhancement of acoustic and thermal insulation of the buildings is an important issue. The aim of the present research was to evaluate the physical, acoustical, and thermal performances of building panels produced by almond skin residues, derived from the industrial processing of almonds. In this paper different mix designs were investigated using polyvinyl acetate glue and gum Arabic solution as binders. Air-flow resistivity sigma and normal incidence sound absorption coefficient alpha were measured by means of a standing wave tube. Thermal conductivity lambda, thermal diffusivity alpha, volumetric heat capacity rho c were measured using a transient plane source device. Finally, water vapor permeability delta(p) was experimentally determined using the dry cup method. Furthermore, a physical characterization of the specimens in terms of bulk density rho(b) and porosity eta allowed to study the correlation existing between the binder and the aggregates and the consequent acoustical and hygrothermal behavior occurring on the different mix designs. The achieved results suggested the investigated materials comparable to the main products currently existing on the market.