Study of the hygroscopic properties of environmentally friendly lightened composites through waste recovery

Abstract

Gypsum-plaster is becoming an ideal binder in the valorisation and recovery of waste for designing more sustainable composites. Nevetheless, the main limitation of plaster lies in its susceptibility to the action of water. In this research, a complete study of the hygroscopic properties of a new material has been carried out, in which plaster material has been partially substituted in mass by dissolved expanded polystyrene waste in percentages of 8.8% to 26.5%. Additionally, fibres from end-of-life tyres have been incorporated at 1.2% by mass to improve the strength and durability of the compounds, achieving a total reduction of up to 28% of the original raw materials. The experimental campaign delves into the water performance of this new plaster composites through mercury porosimetry tests, water absorption by capillarity, total water absorption, water vapour permeability, Karsten Tube penetration, water-stove cycles, as well as the analysis of images obtained by scanning electron microscopy. The main results obtained show a reduction of 97.8% in surface water absorption, as well as a decrease of up to 17.44% in water vapour permeability compared to traditional plaster. Moreover, the developed materials exhibit good mechanical behaviour after undergoing several accelerated ageing cycles. This work highlights the potential of the new plaster composites designed to produce a more sustainable alternative to commercial prefabricated boards and panels, especially suitable for use in interior rooms where high resistance to the action of water is required.