Synergistic Effect of Hybrid Carbon Nanomaterials as Reinforcing Phase on the Physico-Mechanical Properties and Pore Structure Refinement of Cementitious Nanocomposites

In the present study, the enhanced physico-mechanical performance of cement mortar nanocomposites by hybrid graphene oxide-functionalized carbon nanotubes over individual nano additives i.e., graphene oxide and FCNTs as reinforcing phases have been investigated. Graphene oxide (GO) was prepared from ball-milled graphite powder (GP_b) by in-house designed horizontal ball-mill and carbon nanotubes were functionalized by the acid treatment of the pristine multi-walled CNTs. The surface-treated nanofillers were characterized well by FT-IR, SEM-EDX, XRD, AFM, and Raman spectroscopic techniques. The compressive strength of the HCN-CNCs was improved by 43.02% with respect to control sample at the curing age of 90 days for 0.02% HCNs loadings (by weight percentage of cement). This was found to be superior to the strength enhancements of 27.39% by GO and 17.82% by FCNTs at loadings of 0.02 and 0.08%, respectively. SEM images showed compact hydration products in case of cementitious matrices involving hybrid carbon nanomaterial as reinforcing phase. Better hydration of the various phases has also been confirmed by the XRD studies. In addition to the SEM and XRD, the enhancement in the compressive strength has also been interpreted in terms of porosity. Microstructure of the cement mortars was also investigated by Mercury Intrusion Porosimeter to evaluate the effect of HCNs on the porosity and pore size distribution of large capillary pores (>0.1 µm), medium capillary pores (0.01–0.1 µm), and gel pores (<0.01 µm) of the cement matrix. The improvement in the mortar properties using advanced reinforcement at nanoscale can pave a way to better and sustainable construction based infrastructure.