3D printed smart repairs for civil infrastructure

Christos Vlachakis, Lorena Biondi, Marcus Perry, Department of Civil and Environmental Engineering, University of Strathclyde, Glasgow, UK 

Civil structural health monitoring involves the non-destructive evaluation of elements in order to maintain and prolong the lifespan of (typically steel or concrete) infrastructure. This is facilitated by the incorporation of sensing devices. In this research, smart materials for civil infrastructure repairs are being developed. The materials in this project are characterized as “smart” due to their ability to simultaneously sense and repair steel and concrete structures. In order to achieve these properties in a smart material patch, metakaolin-based geopolymers are being employed. As metakaolin geopolymers attain comparable mechanical properties to ordinary Portland cement and favourable adhesive characteristics, they can be used to restore the structural integrity of degraded concrete elements. Geopolymers furthermore exhibit a pronounced electrical conductivity due to the presence of free ions in their matrix. Geopolymers can therefore be used to detect variations in strain and temperature through changes in electrical impedance. In essence, these are repair materials that also enable constant monitoring. In this project, smart materials are being extruded with the assistance of a 3D printer, and will ultimately be robotically applied. The extrusion of smart cement patches via a 3D printer allows greater versatility of design and improved geometrical repeatability. Patch shape and size can be easily adjusted according to the requirements of each given circumstance, while robotics will allow printing in areas with hazards or limited access. In this paper, we will present our latest progress in printing and characterising the mechanical and electronic properties of geopolymer patches, and discuss how raw sensor data can be interpreted into measures of structural health. We will also outline the challenges in the system’s design, and describe the future work required to scale the technology up to real industrial applications.

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