Self-sensing 3D printed repair for concrete substrates

Continuous monitoring allows informed maintenance to more effectively prolong the lifespan of civil infrastructure. In this paper, we outline a 3D printing process for smart materials that could simultaneously support the distributed sensing and maintenance of reinforced concrete structures. The smart material employed in this research is alkali-activated metakaolin. It is already well-known that alkali activated metakaolin can attain comparable mechanical characteristics to ordinary Portland cement and is thus able to repair and restore the structural integrity of damaged concrete infrastructure. However, these materials also exhibit a higher electrical conductivity than conventional cements due to the presence of free ions in their matrix. This allows temperature and strain to be monitored through variations in electrical impedance. Here, we demonstrate additive manufacturing of these materials to allow remote installation, with greater design flexibility and repeatability. In this paper, the electrical response of printed samples is outlined, and we discuss how sensor data can be interpreted to detect strain variations for structural health monitoring applications