Strain sensors can be embedded in civil engineering infrastructures to perform real-time service life monitoring. Here, the sensing capability of piezoresistive cement-based composites loaded with carbon black (CB) particles is investigated. Several composite mixtures, with a CB filler loading up to 10% of binder mass, were mechanically tested under cyclic uniaxial compression, registering variations in electrical resistance as a function of deformation. The results show a reversible piezoresistive behaviour and a quasi-linear relation between the fractional change in resistivity and the compressive strain, in particular for those compositions with higher amount of CB. Gage factors of 30 and 24 were found for compositions containing 7 and 10% of binder mass, respectively. These findings suggest that the CB-cement composites may be a promising active material to monitor compressive strain in civil infrastructures such as concrete bridges and roadways.

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The growing concern in monitoring civil infrastructures, combined with recent technological advances in sensing and information technology led to a concept known as 'smart infrastructures'. Recently, nanotechnology has been contributing with the development of innovative and multifunctional building materials. For example, cementitious composites with specific conductive composition allow the detection of mechanical stresses and may be used not only to build infrastructures but to monitor them as well. In this paper, a stress-sensitive cement composite integrating a conductive carbon black filler (CB) is investigated for traffic monitoring purposes, relying on piezoresistivity. The sensitivity of the composite was evaluated in specific specimens by performing traffic-like loading experiments, at temperatures between 15 °C and 45 °C. Experiments showed linear and reversible piezoresistive responses with average gauge factors registered between 40 and 50 and demonstrated that such composites may act as stress-sensitive materials for traffic monitoring, such as traffic flow, vehicular speed and weigh-in-motion measurements.

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