Electro-mechanical investigations of steel fiber reinforced self-sensing cement composite and their implications for real-time structural health monitoring

Abstract

Self-Sensing Cement Composites (SSC) made from cementitious composites with electrically conductive elements have many applications in structural health monitoring (SHM). Because of their compatibility and endurance, SSC outnumbers traditional piezoelectric and fiber optic sensors in SHM. This study aims to develop a self-sensing composite using steel fibers and silica fume. Silica fume is utilized in the composite to improve strength and accelerate material dispersion. In addition to compressive strength and conductivity, which are crucial for self-sensing characteristics, the research also focuses on piezoresistivity and sensitivity of a composite to have real-time applications in SHM. The performance index approach is used to optimize the SSC with combined strength, conductive and sensing characteristics. Scanning Electron Microscopy (SEM), X-Ray diffraction (XRD), and Energy-dispersive X-ray (EDAX) investigations are carried out to study the morphology characteristics that induce strength and conductivity to the composite. The optimized SSC is embedded at the compression zone, tensile zone, and combined flexure-shear zone (500 mm from beam center) in the beam and at the center of columns to monitor their performance (deflection). According to the research findings, steel fibers increased the compressive strength (= 67.3 MPa) and reduced the resistivity (= 103 Ωcm) of the composite. The piezoresistivity and stress sensitivity of a composite is influenced by the compressive strength of the composite and the dispersion of steel fiber in the composite. Silica fume contributes directly to strength by forming more calcium silicate hydrates (C–S–H) and indirectly to conductivity by permitting the dispersion of conductive materials. The results revealed that an SSC embedded in the compression zone can accurately depict the deflection of the beam than the SSC embedded in the tensile and combined flexural zones of the beam. The developed SSC can lower its resistivity in the beams with a maximum Pearson correlation coefficient between deflection and resistivity as 0.99. However, in this combined flexure and shear zone (500 mm from the beam center), the composite cannot distinguish between rapid and slow reduction in beam deflection. The research inferred that the SSC has a strong relationship with column deflection (=0.94 approx.) up to the development of cracks in the SSC. Finally, after characterization, strength, resistivity assessments, and application in structural components, the steel fibers are identified and justified as potential materials for developing SSC.