Pore Size Distribution

Capillary pores are considerably larger than gel pores, and various pore sizes exist within the hardened cement paste.

In conditions of partial hydration, the paste includes a network of capillary pores, leading to higher permeability and increased susceptibility to damage from freeze-thaw cycles, chemical exposure, and reduced strength.

These issues can be effectively mitigated when the hydration level is sufficiently high to disrupt the existing capillary pore network through the formation of new cement gel, thereby enhancing the structural integrity of the concrete.

In pastes with a low water-cement ratio that is well hydrated, the size of capillary pores typically falls between 0.4 and 2 microinches.

Conversely, in pastes with a high water-cement ratio and the initial stages of hydration, these pores can span from 120 to 200 microinches.

Pores larger than 2 microinches, known as macropores, are believed to play a more critical role in the strength and impermeability of the material.

It has been proposed that analyzing the distribution of pore sizes provides a more accurate assessment of a hydrated cement paste's properties than simply measuring total capillary porosity.