Physico-mechanical and electrical characterization of mortars enhanced with carbon nanotubes and microfibers

The progress in smart mortars has driven the use of conductive materials in lime and cement based composites, particularly for structural health monitoring and preservation. This study makes a novel contribution by investigating the effects of incorporating carbon-based materials, such as carbon nanotubes (CNTs) and carbon microfibers (CMFs), on the physical, mechanical, and electrical properties of lime and cement mortars. Initially, CNTs dispersed in water were characterized by UV–Vis and Raman spectroscopy to ensure dispersion stability and structural integrity. Subsequently, the mortars were tested for workability, water absorption, porosity, bulk density, compressive strength, and electrical resistivity at varying curing times. The dispersion method was effective, ensuring CNT structural stability. Incorporation of CNTs, although reducing workability, promoted greater densification of the cementitious matrix, with decreased porosity and improved electrical stability at concentrations starting from 0.2 %. The best responses in lime mortars were achieved with 0.1 % CMFs, while a 0.05 % content resulted in the greatest mechanical strength gain. The electrical percolation threshold was observed at concentrations of 0.05 % CMFs and 0.2 % CNTs, maintaining electrical stability up to 56 days. Furthermore, in lime mortars, CMFs outperformed CNTs in terms of physical, mechanical, and electrical properties. In cement mortars, although CMFs better preserved workability, CNTs demonstrated superior effectiveness in matrix densification and electrical stability. Thus, the selection of the ideal additive is directly dependent on the type of matrix used. This study identifies CMFs as more suitable for lime based mortars and CNTs as more appropriate for cement based mortars, as evidenced by the experimental results.