Funct. Mater. 2023; 30 (3): 407-412.

The mechanical properties of the pozzolan-added cement material with the addition of nano C-S-H have been studied. A mechanism that influences on them is proposed. X-ray diffraction (XRD), scanning electron microscopy (SEM), and mercury intrusion porosimetry (MIP) were used to characterize the microstructure of the pozzolanic mortar. The results showed a significant effect of property improvement when using nano-sized C-S-H: the compressive strength increased from 22.3 MPa to 33.2 MPa after 7 days. SEM images showed that after the addition of nanosized C-S-H, the matrix became more compact and the number of defects decreased. X-ray analysis confirmed that the addition of nanosized C-S-H increased the amount of C-S-H formed during hydration. The MIP results showed that nanoscale CSH improves the pore structure of the mortar and significantly reduces the porosity. All microscopic measurements showed that nanosized C-S-H accelerates the process of cement hydration and forms more hydration products, which contributes to the modification of the interfacial transition zone of the solution and increases the compactness of the matrix. This is the main reason for improving the initial mechanical properties of the cement-based pozzolanic mixture.