PSI - Issue 83

Samia M. Mohamed et al. / Procedia Structural Integrity 83 (2026) 63–71

68

rGO, CB, GO; best at 0.2% rGO and 2.5% CB

Dogra et al., 2025

Cement-based composite

_

_

Max FCR up to 400%

SF: Silica fume, ACP: Activated carbon, f`c: Compressive strength, ft: flexural strength, MCMF: Milled carbon microfiber, CCMF: Chopped carbon microfiber, FA: Fly ash, FAC: Fly ash cenosphere, LC³: Limestone Calcined Clay Cement, RM: Red mud, UHPFRC: Ultra-high performance fiber reinforced concrete, GP: Graphite powder, ECC: Engineered cementitious composites, rGO: reduced carbon oxide, GO: Carbon oxide. 3. Limitations, Challenges, and Future Directions Despite significant advances in the development of conductive cementitious composites and extrusion-based additive manufacturing technologies, the integration of 3D printing with self-sensing functionality in cementitious materials remains at an early stage of development. The studies summarized in Table 1 demonstrate promising sensing capabilities and mechanical performance; however, several limitations continue to hinder the practical implementation of these materials in structural applications. 3.1. Limited Integration of Printability, Mechanical Performance, and Sensing Behavior One of the primary challenges in developing 3D-printed self-sensing cementitious composites is the simultaneous optimization of printability, mechanical performance, and sensing functionality . Many existing studies tend to focus on one aspect while treating the others as secondary considerations. For example, Wang et al. demonstrated that hybrid carbon-based conductive systems consisting of carbon fibers (CF) and activated carbon powder (ACP) can significantly enhance both compressive strength and piezoresistive sensing behavior in printable cementitious composites, achieving compressive strengths up to 74.9 MPa while maintaining a stable sensing response. However, the mixture design was primarily optimized for sensing performance rather than large-scale structural printability (Wang et al., 2022). Similarly, Liu et al. developed hybrid graphite–carbon microfiber self-sensing composites and reported a GF of 622 with high strain resolution, highlighting the potential of hybrid conductive systems for high-sensitivity sensing (Liu et al., 2024b). Nevertheless, the investigation was conducted at the small-specimen level, and issues related to structural printing, durability, and large-scale fabrication were not addressed. In another study on printable ultra-high performance concrete (UHPC), Liu et al. showed that the addition of graphite and carbon microfibers could increase compressive strength and elastic modulus by 9.8 % and 19.2 %, respectively, while enabling reliable sensing behavior, although the gauge factor of printed specimens was lower than that of cast specimens (Liu et al., 2024a) These findings indicate that a comprehensive design strategy that simultaneously considers rheology, mechanical properties, and sensing behavior is still missing in the current literature. 3.2. Influence of Print-Induced Anisotropy and Interlayer Interfaces Extrusion-based additive manufacturing inherently produces anisotropic microstructures, as the material is deposited layer by layer along a defined printing path. This anisotropy can influence both the mechanical behavior and the electrical conductivity of printed cementitious materials. For example, Wang et al. reported that the strongest piezoresistive response occurred when the loading direction was perpendicular to the printing direction, suggesting that the orientation of conductive fillers and filaments during extrusion strongly affects the sensing response (Choi et al., 2022). Similarly, structural-scale studies have shown that print orientation and interlayer bonding significantly influence both mechanical strength and electrical resistivity. For instance, the mechanical and piezoresistive behavior of 3D-printed self-sensing slab elements was found to vary depending on the printing direction, with compressive strengths reaching 56.02 MPa and resistivity values around 355 Ω ·cm, while the strongest sensing response occurred in the direction perpendicular to the printing path (Sun et al., 2025). Another structural investigation demonstrated that 3D-printed cement-based sensing elements embedded in reinforced concrete beams can successfully capture strain and crack formation during loading, although the sensing performance of printed sensors was lower than that of bulk