Effects of multiscale carbon-based conductive fillers on the performances of a self-sensing cementitious geocomposite

In this study, the effects of multiscale conductive carbon fillers, including carbon nanotubes (CNTs), graphene nanoplatelets (GNPs), and carbon fibres (CFs), on the mechanical and microstructural properties, durability, and piezoresistivity of cementitious stabilised sand (CSS) were investigated. In this route, the surface of the CFs was modified via an oxidation process to improve their interfacial performance and dispersion. An optimum amount of hybrid CNT/GNP with different concentrations of CFs was incorporated into the CSS, and specimens were fabricated using the standard compaction method at the optimum water content. The interfacial properties of the CFs were studied by performing pullout tests and several chemical analyses. The variations in the mechanical and microstructural, durability, and piezoresistivity of the CSS, were investigated by various tests. In addition, the status of the specimens in terms of residual strain and damages was identified by the digital image correlation technique. The results showed a considerable improvement in the interfacial properties of the modified CFs in terms of physical and chemical bonding with the cement matrix. In addition, a combination of 0.17% CNT/GNP (1:1, by weight of dry sand) with 0.75% CF can improve the maximum dry density and mechanical properties, as well as the ductility and durability of the CSS. In addition, using multiscale conductive fillers resulted in a considerable enhancement in the electrical conductivity and piezoresistivity of the CSS. The outcomes indicate the immense potential of CNT/GNP/CF for the development of a sustainable self-sensing cementitious geocomposite.This work was supported by the European Commission-Shift2Rail Program under the project “IN2TRACK3, H2020–S2RJU-CFM-2020, S2R-CFMIP3- 01–2020”. Furthermore, it is partly financed by FCT/ MCTES through national funds (PIDDAC) under the R&D Unit of the Institute for Sustainability and Innovation in Engineering Structures (ISISE), under reference nº. 101012456, as well as under the R&D Unit of the Centre for Textile Science and Technology (2C2T)