Improved interfacial strength of SiO2 coated carbon fiber in cement matrix

To improve the interfacial properties of carbon fiber in cement matrix, a thin SiO2 layer was coated onto carbon fibers through the condensation and polymerization of the tetraethyl orthosilicate under alkaline conditions. The morphology and chemical composition of the surficially grown SiO2 were characterized and analyzed. The surficially grown SiO2 layer reacted with Ca(OH)2 to form calcium silicate hydrate, which condensed the fiber-matrix interface. A single carbon fiber pullout from cement matrix test was conducted to evaluate the merit of surficial grown SiO2 on interfacial properties. Chemical debonding energy and frictional bond strength were obtained based on the pullout curves. The experimental results showed that the chemical debonding energy and frictional bond strength of the modified carbon fibers were significantly enhanced with respect to those of the plain carbon fiber, and this effect was primarily attributed to the improvement in interfacial hydration products that benefited from the reaction between surficial-coated SiO2 and Ca(OH)2.