3D-printed smart reinforced beam for in-process monitoring

Recent advances in additive manufacturing have opened new opportunities for concrete constructions in civil engineering, offering design freedom, rapid prototyping, and reduced dependence on traditional formwork. However, the reliability of printed components is often compromised by process-induced uncertainties, such as inconsistent interlayer adhesion, interruptions during printing, and material inhomogeneity. These issues create challenges for ensuring structural quality and durability in large-scale applications. Embedding sensing functionalities directly within the printed elements provides a pathway to address this limitation by enabling in situ performance tracking and real-time quality assessment. In this work, we demonstrate the local functionalization of 3D printed concrete components using a hybrid 3D printing strategy, with the objective to enable in-process monitoring. To do so, graphite powder and carbon microfibers were incorporated into cement-based mixtures to impart self-sensing capabilities through piezoresistive behavior, producing a self-sensing composite. The technology was validated on a reinforced concrete beam, in which the self-sensing composite layer was deposited at the bottom and transitioned into a conventional cementitious mix along the height. Time-series measurements were acquired during the printing process to assess the capability of the self-sensing unit at monitoring the additive manufacturing process. Measurements exhibited a marginally decreasing resistance for each additional layer, capturing the material state. The temporal evolution in the material state was successfully modeled, thus representing a first step toward the development of a digital twin framework for in-process monitoring of additively manufactured concrete components.