Application of a Nano-Silica Coating on Fly Ash Concrete Controlling Fungal Biofilm Based Biodeterioration

Fly ash concrete (FAC) biodeterioration caused by fungal biofilm is a major problem for the building sector. Both biodeterioration of FACs and the effectiveness of nanosilica coating for its prevention were assessed in laboratory conditions. According to preliminary tests, Aspergillus tamarii caused higher biodeterioration on FAC than Aspergillus niger. In subsequent tests, FAC cubes (10 cm × 10 cm × 10 cm) were utilised to create three setups: control (Set-C), biodeterioration infected with A. tamarii (Set-B), and preventive set (Set-P), which contained the growth of both A. tamarii on nanocoated cubes. After 6 months, the Set-B cubes had obvious fungal colonisation and surface damage, while the Set-P cubes exhibited less degradation. The Set-P cubes showed less calcium ion leaching and improved compressive strength than the Set-B. The concrete in Set-B lost 17.42% of its compressive strength, compared to 7.34% in Set-P. The biodeterioration caused by A. tamarii is successfully prevented by the silicon oxide nanocoating. The calcium leaching from the FAC as a result of carboxylic acids generated by the studied fungus was confirmed by the FTIR and EDXRF observation. This work reveals the mechanisms and potentiality of nano-silica coatings on concrete to control fungal biofilm growth.