Anti-biofouling properties of graphene-based nanoadditives in cementitious mortars

Biofouling is a striking pathological manifestation in the facade elements that can impair the building aesthetics and compromise the integrity and durability of the building envelope. Studies involving the use of graphene family materials (GFMs -graphene, graphene oxide, reduced graphene oxide) in cementitious matrices have already been developed, showing that graphene can improve the mechanical properties of cement composites. As far as it was observed until now, there are no studies of graphene in cement materials focusing on self-cleaning. To combine different properties, such as mechanical strength, workability and self-cleaning, we show the potential of the nanocarbon family as a multifunctional material for construction industry. Other nanomaterials, such as titanium oxide, zinc oxide and silver nanoparticles are already used for self-cleaning. For silver nanoparticles, cost can be an impediment, while TiO2 and ZnO need to be applied to the light-exposed environment to perform photocatalysis. However, some problems of biofouling in buildings occur in the absence or low incidence of light, which indicates the need for new materials and multifunctionalities. Thus, that can be achieved by combining photocatalysts with materials from the nanocarbon family. Here, graphene and CdS-based nanoadditives were studied as self-cleaning alternatives for mortars. Thereby, two approaches were employed to analyze these properties: 1) Biofilm degradation and accelerated microalgae growth methods; 2) Photodegradation of methylene blue. The best result achieved for graphene presented only 2.5% of microalgal coverage by the end of the accelerated microalgae colonization assay, against 87.0% of surface colonization of the control samples. The results for graphene nanoadditive on mortar show a superior result in terms of microalgae growth inhibition, acting through mechanisms other than photocatalysis and exhibiting efficiency even in the absence of lighting. Furthermore, CdS/ graphene-based nanoadditives presented a synergistic effect. This resulted in better photo -catalytic responses for the mortars, when compared with those containing only CdS-based nanoadditives in methylene blue degradation tests.