Combination usage of nano-SiO2-coated steel fiber and silica fume and its improvement effect on SFRCC

Abstract

To further improve the fiber-matrix interfacial properties and enhance the macro-mechanical performances of steel fiber reinforced cement-based composite (SFRCC), two effective modification methods, nano-SiO2-coated steel fiber (NSF) targeted at the fiber-matrix interface and silica fume targeted at cement matrix, were tried to use together. The modification effects of NSF, silica fume and their combination usage were characterized and analyzed at multi-levels. Backscattered electron image analysis (BSE-IA) was used for micro microstructure characterization and the micro-hardness test was employed to evaluate the micro-mechanical property. A fiber pull-out test was drawn up and the interfacial bond properties, including the pull-out load-displacement curve, average bond strength and pull-out energy, were obtained. Flexural and compressive tests were conducted and the bending performance, flexural and compressive strength were focused on. The results show that the modification mechanisms of NSF and silica fume on SFRCC are quite different in that the one-way modification of NSF is from interface to bulk paste whereas that of silica fume is from bulk paste to interface. Both two methods improve the microstructure and performance of SFRCC effectively. Combination usage takes full advantage of the two modification methods, matches the improvement of different micro zones by two-way modifications, improves the interfacial bond properties and thereby achieves the further enhancement effect on macro performance.