Material properties of cement paste and mortar, modified with N-doped mesoporous carbon spheres (NMCSs)

The addition of nitrogen doped mesoporous carbon spheres (NMCSs) to Portland cement-based materials was studied as an approach to produce materials of desired properties. Lower electrical resistivity and higher compressive strength were recorded in the presence of NMCSs, while the addition of a dispersion agent (Pluronic F127), caused an increase in electrical resistivity and strength reduction. This performance was related to the variation in zeta potential and hydrodynamic radius of NMCSs in alkaline medium. The zeta-potential of NMCSs was defined by the non-ionic surfactant F127. This led to a “poisoning” of the active NMCSs surface, consequently hindering the interaction of NMCSs with the cement-based material. Therefore, F127 is a non-suitable dispersing agent. In contrast, the presence of NMCSs alone enhances the desired cement-based materials properties, where reduced electrical resistivity and increased compressive strength were achieved, while cement hydration and pore network development were maintained close to NMCSs-free specimens.