Development of piezoresistive cement-based sensor using recycled waste glass cullets coated with carbon nanotubes

Different from widely exploring the application of waste glass to replace natural aggregate or cement powder, this study firstly utilized waste glass cullets coated with carbon nanotubes (CNTs) as conductive fillers to develop novel self-sensing cement-based sensors. The coating efficiency of CNTs and self-sensing properties were also investigated in terms of workability, water absorption, mechanical properties, electrical resistivity and microstructure. The results show that CNTs are attached to the surfaces of waste glass particles, especially the smallsize waste glass particles with high roughness. Workability decreased significantly with the increased waste glass. Cementitious mortar with sand replaced by CNTs-coated waste glass exhibited the highest flowability when the replacement ratio was 25%. Moreover, the water impermeability continuously increased with the content of waste glass. The compressive strength was higher than that of the control mortar, which reached the highest with 50% waste glass content. Additionally, an excellent piezoresistivity was achieved for cement-based sensors with CNTs-coated waste glass particles for the self-monitoring of stress magnitude and failure. The CNTs are uniformly distributed well in the cement matrix by attaching the surfaces of waste glass particles, thus the conductive passages are formed in cement-based sensors for structural health monitoring.