Research Article Stainless Steel Microfibers for Strain-Sensing Smart Clay Bricks Antonella D’Alessandro , Andrea Meoni, and Filippo Ubertini Department of Civil and Environmental Engineering, Via G. Duranti 93, 06125 Perugia, Italy Correspondence should be addressed to Antonella D’Alessandro; antonella.dalessandro@unipg.it Received 13 February 2018; Accepted 8 July 2018; Published 5 August 2018 Academic Editor: Fanli Meng Copyright © 2018 Antonella D’Alessandro et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Life cycle monitoring of structural health of civil constructions is crucial to guarantee users’ safety. An optimal structural health monitoring system allows to automatically detect, locate, and quantify any damage in structural elements, thus anticipating major risks of local or global failures. Critical issues affecting traditional monitoring systems are sensors’ placement, hardware durability, and long-term reliability of the measurements. Indeed, sensors’ deployment is crucial for an effective investigation of the static and dynamic characteristics of the structural system, whereby durability and long-term stability of sensing systems are necessary for long-term monitoring. A very attractive solution to some of these challenges is developing sensors made of the same, or similar, material of the structure being monitored, allowing a spatially distributed and long-term reliable monitoring system, by the use of self-sensing construction materials. Within this context, the authors have recently proposed new “smart clay bricks” that are strain-sensing clay bricks aimed at embedding intelligent monitoring capabilities within structural masonry buildings. While previous work focused on smart bricks doped with titanium dioxide and using embedded point electrodes, this work proposes an enhanced version of smart bricks based on the addition of conductive micro stainless steel fibers that possess higher electrical conductivity and a more suitable fiber-like aspect ratio for the intended application, as well as plate copper electrodes deployed on top and bottom surfaces of the bricks. The paper thus presents preparation and experimental characterization of the new smart bricks. The influence of different amounts of fibers is investigated, allowing the identification of their optimal content to maximize the gauge factor of the bricks. Both electrical and electromechanical experimental tests were performed. Overall, the presented results demonstrate that the new smart bricks proposed in this paper possess enhanced strain-sensing capabilities and could be effectively utilized as sensors within structural masonry buildings. 1. Introduction Structural health monitoring (SHM) of buildings is a very attractive technology for enhancing safety of users and occu- pants [1–3]. Among different construction types, traditional masonry structures, including historic and monumental buildings, entail the greatest monitoring challenges due to the peculiar heterogeneity and complexity of their compo- nents, to material nonlinearity and to the possible activation of both local and global failure mechanisms. Traditional sensing systems for SHM are made of materials that are very different from those of the monitored constructions. Further- more, they are usually applied on the external surface of the elements and have durability drawbacks. The high cost of such sensing systems is also a quite often limiting issue. In the last few years, much scientific attention has been devoted to smart construction materials exhibiting self-sensing capa- bilities [4–6]. Nevertheless, only a few of those works have been focused on smart materials suitable for structural appli- cations, with the majority of the contributions devoted to cement-based materials and concretes [7–9]. The sensing ability of smart materials is typically obtained by doping tra- ditional matrices with conductive nano- or microfillers. Most of the researches concern carbon-based inclusions, such as carbon nanotubes and carbon fibers [10]. The authors have studied the behavior of cementitious materials with carbon additions with a specific attention to dynamic strain sensing [11] and recently presented a new structural multifunctional Hindawi Journal of Sensors Volume 2018, Article ID 7431823, 8 pages https://doi.org/10.1155/2018/7431823