Piezoresistive sensing of cementitious composites reinforced with shape memory alloy, steel, and carbon fibres

The piezoresistive behaviour of self-compacting cementitious composites incorporating superelastic nickel-titanium shape memory alloy fibres (SMAFs), steel fibres (SFs), and carbon fibres (CFs) is presented. Piezoresistivity in the cementitious composites allows sensing stress and strain under cyclic compression. The matrix of composites consists of cement, fly ash, ground-granulated blast-furnace slag, and silica fume as the binder and both fine aggregate. Six fibre volume fractions ranging from 0.25% to 1.50% at intervals of 0.25% are considered for SMAFs and SFs while CFs are added at low volume fractions ranging from 0.1% to 0.6% at intervals of 0.1%. First, fresh and mechanical properties of the developed composites are discussed. Then, the piezoresistive sensitivity, repeatability, and gauge factor are analysed under cyclic compressive stress with an amplitude of 10 MPa. Results show noticeable polarisation in composites with SMAFs and SFs, compared to CF reinforced composites. A maximum gauge factor of 935 and the highest correlation coefficient between fractional change in resistivity and compressive strain are obtained for the composite containing 0.6% CFs.