Biofouling resistance and practical constraints of titanium dioxide nanoparticulate silane/siloxane exterior facade treatments

This paper presents the evaluation of titanium dioxide nanoparticulate enhanced silane/siloxane emulsions and their resistance to biofouling by algal colonisation. Varying amounts of titanium dioxide nanoparticulates were incorporated into silane/siloxane emulsions and bioreceptivity assessed. A culture streaming study was conducted to evaluate each treatment using mortar samples. Characterisation of the treatments included assessment of the porosity, surface roughness, sorptivity, hydrophobicity, treatment depth and visual aesthetical alteration. The results showed that titanium dioxide nanoparticulate incorporation did not adversely alter treatment penetration. All titanium dioxide treatments imparted superhydrophobic water repellent attributes while effectively conserving the morphology of the substrate. It was concluded that the reduced bioreceptivity observed primarily stemmed from the nanoparticulates ability to photocatalytically breakdown contaminants and that only a small concentration was required to achieve vastly significant improvements at concentrations <0.5 %wt. The presented treatments had negligible impact on visual aesthetics of the substrate making them ideal for future retrofit and heritage remediation schemes.