Effect of reduced graphene oxide, alumina and silica nanoparticles on the deterioration characteristics of Portland cement paste exposed to acidic environment

Acid attack on cement concrete results in the development of a degraded layer surrounding the unaffected material, which causes a deterioration of mechanical properties. The effect of reduced graphene oxide, alumina and silica nanoparticles on the deterioration characteristics of 28-day cured cementitious pastes after storage in 0.5 moL/L HNO3 solution for a period of 56 days is reported in this paper. Samples were collected from the degraded pastes at different time periods and then characterised using various techniques like scanning electron microscopy with energy dispersive spectroscopy, optical microscopy, thermogravimetric analysis, mercury intrusion porosimetry, X-ray computed tomography and nanoindentation. While the porosimetry results showed that the presence of reduced graphene oxide and nano alumina decreased the amount of capillary pores (10 nm-10 μm) by up to 46% and 51% than the control paste after storage in acidic solution for 28 days, the details of the relative zones formed in the paste along with their characteristics were revealed by the microscopy and nanoindentation techniques. Overall, the results suggest that the presence of these nanomaterials refined the pore structure of the cementitious matrix and thereby increased the resistance to leaching of calcium ions from the binder phases exposed to aggressive aqueous media.