Steel Reinforcing Bar and Steel Fibers Content Effect on Tensile and Electrical Behaviors of Strain-Hardening Cement Composite (SHCC) with MWCNTs in Direct Tension

Featured Application The development of a cement-based strain-detecting sensor and structural health monitoring (SHM) for civil infrastructures using cement-based strain-detecting sensors. This research examines the influence of an embedded steel reinforcing bar and micro steel fibers on the tensile and electrical properties of polyethylene (PE) fibers reinforced cement composite dumbbell-shaped specimens with multi-walled carbon nanotubes (MWCNTs) in direct tension. The cement composites are reinforced with 0.75 vol.% PE fibers to achieve a strain-hardening performance in direct tension and 1.0 wt % MWCNTs are incorporated to give the electrical conductivity into the cement composites. To investigate the steel bar and steel fibers effect on the electrical behavior of synthetic PE fiber reinforced strain-hardening cement composites (PE-SHCCs), a round bar with a diameter of 4 or 7 mm is placed at the center of specimen's cross-section. Additionally, steel fibers' content of 0, 0.5 and 1.0 vol.% are added into the PE-SHCC mixtures. The test result indicates that the addition of steel fibers improves the tensile strength and electrical behavior of synthetic PE fiber reinforced SHCC. The self-sensing ability of PE-SHCC with 1.0% steel fibers is improved by the presence of the embedded steel bar before an initial crack while the reinforced PE-SHCC specimens were less sensitive as the tensile strain increased after the initial crack. The optimal linear regressions between fractional changes in resistivity (FCR) and tensile strain were achieved for PE-SHCC containing 1.0% steel fibers.

Automated summary

This research developed a cement-based strain-detecting sensor for structural health monitoring of civil infrastructures, and investigated the effects of embedded steel reinforcing bars and micro steel fibers on the properties of synthetic PE fiber reinforced cement composites. The study found that the addition of steel fibers improved the tensile strength and electrical behavior of the composite materials, and optimal linear regressions were achieved for samples containing 1.0% steel fibers in terms of changes in resistivity and tensile strain.