Fly Ash Concrete Specimens Admixed with Nanoparticles and Their Interaction with Seawater

This study is on fly ash (FA) concrete admixed with ${\mathrm{TiO}}_2$ nanoparticles (FAT), ${\mathrm{CaCO}}_3$ nanoparticles (FAC), and an equal ratio of ${\mathrm{TiO}}_2$ and ${\mathrm{CaCO}}_3$ nanoparticles (FATC) were exposed to seawater for 365 days in order to find the attachment of macrofoulants on their surface. The pH reduction studies were carried out in order to determine concrete deterioration in seawater, the results showed that FA specimens had more pH reduction than FAT, FAC and FATC. Total viable count, epifluorescence microscopy and denaturing gradient gel electrophoresis (DGGE) analysis confirmed the intensity of bacterial attachment and its diversity on FA, FAT, FAC, and FATC specimens. A systematic and comparative analysis predicted the overall relationship in terms of the dominant bacterial species on the different fly ash concrete specimens. To determine the biodeterioration of the fly ash concrete specimens in seawater, we used thermography experiments to evaluate the regions affected by bacteria on mortar specimens and confirmed that FA and FAC had more degradation and that FAT and FATC were the least degraded. Laser Raman Spectroscopy was interesting to find the white micron-sized particles of sulphur on FAC, FAT, and FATC specimens after 365 days immersed in seawater. We used a confocal laser scanning microscope to estimate the thickness of biofilm growth on FAT (13.91 0.38 mm), FATC (21.64 0.22 mm), FAC (33.56 0.26 mm), and FA (43.36 0.10 mm) specimens. The results showed that FAT and FATC specimens were the superior specimens, with enhanced biofouling and biodeterioration resistance in a seawater environment.

Fly ash is a waste material from thermal power plants and is used as a supplementary cementitious material in the construction industry. However, fly ash concrete has a slow hydration process and early strength problems. To overcome these problems, we used ${\mathrm{TiO}}_2$ and ${\mathrm{CaCO}}_3$ nanoparticles to enhance the properties of fly ash concrete. Nanoparticles have a high surface area and unique functional properties such as maintaining concrete pH, reducing porosity, enhancing pozzolanic activity, and so forth. In this study, we used ${\mathrm{TiO}}_2$ and ${\mathrm{CaCO}}_3$ nanoparticles to improve the strength of fly ash concrete and provide it with antibacterial properties. This study is significant in advancing our knowledge of fly ash concrete modified with nanoparticles and exposed to seawater with respect to its mechanical properties, durability, and antibacterial properties. Addition of nanoparticles upgraded the fly ash concrete towards its practical applications.