Effects of hybrid carbon and steel fibres on self-sensing and electromagnetic wave absorbing properties of concrete

Besides the enhancements on tensile strength and anti-shrinkage cracking, well-designed conductive fibres reinforced cementitious materials can obtain electromagnetic properties, like electrical conductivity and electromagnetic wave absorption property. However, the relationships among the physical parameters of fibres, the functional performances and the stress conditions of the composite matrix as the key items for improving the electromagnetic properties of cementitious materials is yet unclear. In this work, carbon fibres (CFs) with three different sizes and typical steel fibres are chosen to design the hybrid fibres reinforced concrete, and the factors concerning conductivity and electromagnetic wave absorbing properties in the range of 2–18 GHz are investigated. The percolation thresholds of different CFs in concrete and the different loading processes impact the piezoelectric self-sensing and electromagnetic wave absorption properties in different wave frequency bands. Compared with the fibres’ type, the larger length to diameter ratio of CFs shows more prominent contribution to concrete conductivity. The presence of steel fibres weakens the self-sensing ability and the electromagnetic wave absorption at frequency bands of 4–8 GHz concrete containing CFs. This work proposes a potential balancing rule between the mechanical and electromagnetic properties of cementitious matrix with the hybrid conductive fibres. • Length-to-diameter ratio and content of carbon fibres affect piezoelectric self-sensing behavior of concrete. • Sensitivity of resistance change is more crucial when concrete suffers from cyclic compressive loading. • Conductivity of fibres is not aligned with electromagnetic wave absorbing performance of concrete.