Using sol-gel deposition of nanosilica to enhance interface bonding between sisal fiber and ultra-high performance concrete

A new idea of using sol-gel method deposition of nanosilica on sisal fibers for improving the interface bonding with ultra-high performance concrete (UHPC) was suggested in this study. The change in surface microstructure, chemical groups, surface roughness, thermal degradation process, phase composition, and tensile strength of modified sisal fiber were characterized. Moreover, the fiber modification on early hydration, bond performance, mechanical performance, and autogenous shrinkage of UHPC was further explored. The results showed that nanosilica was successfully coated on sisal fibers, and these nanosilica particles accelerate the early hydration of mixtures. The bond strength (pullout energy) was increased by 28.0% (40.8%) by nanosilica deposition. Consequently, the flexural strength and toughness of UHPC incorporating nanosilica-modified sisal fibers were 9.8% and 40.5% higher than those of untreated sisal fibers reinforced UHPC. Furthermore, the shrinkage-reducing effect of sisal fibers after deposition of nanosilica was increased by 11.5% compared with the untreated fibers. Therefore, nanosilica deposition is a promising method for enhancing the bond performance between plant fiber and UHPC matrix.