A feasible re-use of an agro-industrial by-product: Hazelnut shells as high-mass bio-aggregate in boards for indoor applications

The present work investigates the feasibility of producing boards, with unconventional materials, namely \nhazelnut shells as a high-mass bio-aggregate and a sodium silicate solution as a no-toxic adhesive, and discusses \npossible applications based on an extensive characterization. The aim is to define a feasible reuse of a largely \nproduced agro-industrial by-product to reduce the high environmental impact caused by both the construction \nand the agriculture sectors, by proposing a building composite that improves indoor comfort. The presented \ncombination of aggregate-adhesive generated a product with characteristics interesting to explore. The thermal \nconductivity is moderated, and the composite achieved values of σmax = 0.39 N/mm2 for flexural strength and \nσmax = 2.1 N/mm2 for compressive strength, but it showed high sorption capacity with a moisture buffering \nvalue of about 3.45 g/(m2 %RH), and a peak of sound absorption between 700 and 900 Hz. Therefore, the \nboards’ most promising performance parameters seem to be their high hygroscopicity and acoustic absorption \nbehaviour, namely in the frequency range of the human voice. Hence, the proposed composite could improve \nindoor comfort if applied as an internal coating board.