Characterization of agro-wastes to be used as aggregates for eco-efficient insulation boards

Abstract

This work derives from the awareness of the environmental impacts caused by the construction sector. Since building productsare one of the main causes of this issue, the incremental use of local natural eco-friendly materials can moderate this problem,guaranteeing lower energy consumption for production and transport. Nowadays, research is increasingly focused on thepossibility of using bio-wastes to produce several materials and products such as plasters, bricks, boards, binders and glues. Theycan secure both more sustainable building practices and contribute to solve the problems of disposal of wastes, another cause ofthe environmental impacts.The present work focuses on the characterization of some bio-wastes to assess their viability as aggregates for eco-efficientinsulation boards. Knowing the properties of the raw materials allows making a more conscious choice of composite formulation saccording to the final requirements of the boards. For this reason, the bio-wastes from agricultural practices (agro-wastes) werestudied individually. To evaluate their properties, the analysis was carried out according to RILEM Technical Committee 236 -BBM,“Bio-aggregate-based building Materials” document, past literature studies and European Standards. The considered propertieswere loose bulk density, grain size distribution and thermal conductivity.Four agro-wastes were chosen: spent coffee grounds, grapes press waste, olives press waste and hazelnut shells. Maritime pine(Pinus pinaster Ait.) chips were included as control material. They have been considered both for their potential use to produceinsulation composites and for their world production, focusing on Euro-Mediterranean countries. This region was chosen takinginto account where the future research will be carried out and the advantages of employing local materials. In addition, buil dingsof Euro-Mediterranean countries have historically low insulation performance due to the mild climate; however, climate changeand other factors have led to the recognition by the users of some periods of poor indoor hygrothermal comfort. The bibliographicresearch allowed identifying a gap as concerns the characterization of these agro -wastes.Both the testing methods and the properties of the considered materials are presented and discussed. In addition, the obtaine dresults are compared with the ones of already studied materials, such as rice husk, hemp shiv and cork. Results show that thechosen materials do not have excellent insulating properties if considered individually but may probably be used to produce eco-efficient boards. The combination of them with other materials could guarantee building composites with good thermal insulationperformances. The spent coffee ground differs greatly from the other bio-wastes and it seems to be more appropriate as a fineaggregate. Future research will deepen these studies and develop composites having adequate characteristics as insulationboards.