Strength, energy absorption capability and self-sensing properties of multifunctional carbon nanotube reinforced mortars

The development of multifunctional self-sensing mortars reinforced with multi wall carbon nanotubes (MWCNTs) is herein carried out. The purpose is twofold: to determine the impact of nano-modification on the strength, the stiffness, and the toughening effect that MWCNTs can provide; and to evaluate the multi-functionality and smartness of cement mortars, reinforced with 0.08, 0.1, 0.3 and 0.5 wt% of cement well-dispersed MWCNTs. The experimental determination of the mechanical properties of 3, 7 and 28 d nanomodified mortars was achieved through three point bending, uniaxial compression, and fracture mechanics experiments. The evaluation of the smartness of the nanoreinforced mortars was achieved by measuring the fractional change in the electrical resistance of specimens, induced by external cyclic compressive loading in the elastic region. The excellent reinforcing capability of MWCNTs is demonstrated by a significant improvement in flexural strength (87%), Young's modulus (92%), flexural toughness (83%), first crack strength (64%) and first crack toughness (65%). Results from piezoresistivity experiments confirm that the nanoreinforced mortars exhibit an increased change in resistivity under cyclic compressive loading, which is indicative of the amplified sensitivity of the material in strain sensing.