Enhanced interfacial bonding in cement composites through electrophoretic deposition of nano silica on carbon fibers

Carbon fiber (CF) is widely used in CF-reinforced cementitious composites due to its remarkable mechanical qualities and great durability. Nonetheless, a primary limitation in these composites is the suboptimal interfacial adhesion between the cementitious matrix and the naturally hydrophobic CFs. This inadequacy hinders the effective exploitation of CF's high tensile strength. The current study focuses on the electrophoretic deposition of calcium salts and nano-silica (NS) onto CFs as a strategy to ameliorate this interfacial strength. This study investigated the effect of this modification on the tensile strength and modulus through single fiber tensile testing. Additionally, a series of single fiber pull-out experiment were conducted to assess the alterations in interfacial bonding strength and debonding energy post-modification. In addition, the functional groups and elemental composition for the modified CFs were characterized via Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). Complementary to this, X-ray Photoelectron Spectroscopy (XPS) and Elemental Determination System (EDS). The findings delineate that the deposition product NS adheres to CF surfaces, thereby enhancing the physical anchoring impact and frictional bond strength. On the other hand, the chemical relationship between the CF and the cement is formed through the reaction of silica volcanic ash. NS presence on the CF surfaces facilitates a reaction with Ca(OH)2 in the cement, forming Calcium-Silicate-Hydrate (C-S-H). This reaction product efficaciously fills the interface, substantially fortifying the Interface Transition Zone (ITZ) and consequently improving the interfacial bonding efficacy.