Self-diagnostic lime-pozzolan-cement restoration nanocomposites: Effect of graphene modification and cyclic loading level under compression

In the present study, graphene oxide (GO), reduced graphene oxide (rGO) and carboxylated graphene (GCOOH) have been incorporated in lime-pozzolan-cement pastes, aiming to develop self-sensing binders that would be used for restoration applications. The mechanical and electrical properties of the newly-developed nanocomposite pastes were examined and compared against the respective properties of a reference paste. The incorporation of the different types of graphene nanostructures significantly increased the compressive strength of all the investigated pastes, while the highest increase was noted for the rGO reinforced paste (+33%). The addition of GO and rGO increased by 14 % and 7 %, respectively the flexural strength of the pastes, while no improvement was noticed for the GCOOH addition. On the contrary, the GCOOH addition enabled the paste to exhibit excellent piezoresistive properties. In fact, a 70 % fractional change in electrical resistance was noticed under cyclic loading - unloading at a level of 50 % of the compressive strength. The rest of the mixtures investigated, showed lower fractional electrical resistance change under the same loading protocol.