Biological colonisation in bio-materials and composites with different bio-binder combinations

The increasing demand for sustainable and biodegradable materials in the construction industry highlights the importance of developing circular bio-based building materials that align with the principles of circular bioeconomy. This study forms part of a broader investigation aimed at developing novel construction materials with suitable thermal and acoustic performance. In this context, the present work focuses on evaluating the biological colonisation susceptibility of several natural organic materials in raw form and when used with bio-binder’s, with particular attention to their fungal resistance in humid environments. The studied materials are rice husk, rice straw, Posidonia oceanica and sunflower stalk, alone and in combination with three different binders: arabic gum, xanthan gum and sodium alginate. Fungal resistance was tested exposing samples for four weeks under controlled temperature and relative humidity conditions, allowing quantification of mould growth. Results indicate that the tested unbound organic materials are highly susceptible to fungal colonisation. However, fungal proliferation could be significantly reduced by the addition of binders. Among the binders tested, sodium alginate showed the highest effectiveness in limiting fungal growth for all the tested materials, especially when combined with Posidonia oceanica , which presented the lowest bio-colonisation susceptibility. On the other hand, rice husk and sunflower stalk showed the highest fungal susceptibility, even with the application of binders. The results of this work contribute to a better selection of bio-materials and binders in order to enhance durability and sustainability for bio-based construction composites, contributing to the implementation of circular economy strategies in the built environment. • Fungal susceptibility was assessed in four bio-based materials, both raw and combined with natural binders. • Unbonded materials exhibited highest mould growth in early weeks under controlled humidity and temperature. • Composite with sodium alginate showed minimal fungal growth, particularly when combined with Posidonia oceanica. • ANOVA and Tukey's post hoc test confirmed statistically significant material-binder interactions on fungal development. • The study supports development of durable and eco-efficient insulation bio-based materials.