Comparison of nano reinforcements on cement mortar deterioration under different corrosive environments

Concrete in critical infrastructure, such as nuclear power plants, is frequently exposed to aggressive environments where external sulfate attack poses a significant threat. This study investigates the sulfate degradation mechanism of nano-enhanced mortar incorporating different concentrations of graphene nanoplatelets and multi-walled carbon nanotubes (MWCNTs) under ambient temperature (N2F), high temperature (50°C) (N5F), and combined sulfate-chloride exposure (CN2F). The evolution of properties (e.g., mass, volume, resistivity, UPV, compressive and flexural strength) of samples during curing and post-exposure was monitored and compared with ordinary Portland cement (OPC) samples. After curing, 0.1% graphene and 0.05% MWCNT additions showed maximum compressive strength (59.5 MPa, 61.3 MPa, respectively) and durability. Nano-enhanced samples under N2F showed a three-stage degradation mechanism, which was different from OPC samples. The N2F showed initial pore blocking and densification, followed by initiation of cracking. The N5F exposure regime followed the same mechanism with increased densification due to accelerated hydration. CN2F exposure regime intensified ionic transport and reduced resistivity further, but nano-modified mortars demonstrated improved crack control compared to OPC. Microscopic analysis showed the presence of sulfate reaction and crack bridging. Optimal nano-addition (NG10 and NC5) marks a critical threshold where durability is no longer compromised by early crack-driven degradation, enhancing long-term durability. The eco-feasibility of these materials was studied under aggressive environments.