Advances in Electrical Characterization Techniques for Smart Construction Materials in SHM Applications for Masonry Buildings

It has been shown that incorporating an adequate amount of electrically conductive fibers into structural mortars and clay bricks, near the percolation threshold, improves their ability to monitor local load redistribution, leading to damage-sensing capabilities. Moreover, reducing the fiber concentration allows for the detection of piezo properties, which may include piezoresistive, piezocapacitive, or piezoelectric behaviors. This topic is of specific interest in this work, where we examine different electromechanical characterization techniques to study various types of fillers for composite mortars and bricks, including carbon-based materials (carbon nanotubes, microfibers, graphene), steel fibers, and bioinspired structures. The construction materials incorporated in our research consist of cement pastes, mortars, and clay. All those mixes can be classified into percolated and non-percolated materials. The first type of material (percolated) has demonstrated capabilities for damage sensing, while the second material (non-percolated) exhibits a focus on electromechanical properties. In both cases, the key insight is the sensitivity of the construction material. To find out those interesting capabilities, it has been necessary to incorporate different electrical approaches, such as biphasic square, open circuit potentiometry and electrical impedance spectroscopy (EIS). Furthermore, the composition, geometry and number of electrodes, as well as the acquisition system have several implications on the electrical response. Electrical and mechanical measurements must be interpolated based on their respective timestamps, and then correlated and analyzed across both elastic and plastic regions. Additionally, compression and bending mechanisms were applied using ramp and square cyclic loading signals, with frequencies below 5 Hz, depending on the type of characterization performed. Following this logic, we have developed experimental methodologies to perform electromechanical characterizations and constructed models to physically explain the parameters emerging from these electro-mechanical correlations.