Multifunctional 3D-printed ultra-lightweight engineered cementitious composites: mechanical properties and self-sensing function

This paper initially developed and investigated multifunctional 3D-printed ultra-lightweight engineered cementitious composites (3DP-ULW-ECC), designed specifically for smart infrastructure applications. Its mechanical properties and self-sensing behaviour were systematically evaluated. Calcined petroleum coke (CPC) was incorporated as a conductive material to improve its piezoresistivity. A comprehensive experimental programme, including uniaxial compressive tests, uniaxial tensile tests, and flexural tests, was conducted. 3DP-ULW-ECC had higher compressive strength (achieving 82 MPa) than cast specimens, and both cast and printed ULW-ECC exhibited densities below 1500 kg/m³. The tensile strength and strain capacity of printed ULW-ECC decreased by 17 % and 18 % compared to those of cast ones, respectively. The compressive and three-point bending tests revealed significant anisotropy in 3DP-ULW-ECC, with specimens in the Z direction exhibiting the best compressive and flexural performance due to well-aligned fibre orientation. 3DP-ULW-ECC exhibited stable, repeatable, and reliable self-sensing behaviour under various loading conditions. The self-sensing performance of 3DP-ULW-ECC was worse than that of cast ULW-ECC due to the nonuniform distribution of pores. The mechanisms of piezoresistivity and its anisotropic effect were revealed and elaborately explained. By considering the anisotropy of both mechanical and self-sensing behaviour, 3DP-ULW-ECC is suggested to be loaded in the Z direction.