Nitrogen adsorption and mercury intrusion porosimetry of hydrated portland cement pastes

Abstract EN

The pore structure of well-hydrated Portland cement pastes of 0.4, 0.6, and 0.75 water-to-cement (W / C) ratios was investigated by the nitrogen sorption and mercury intrusion porosimetry (MIP) techniques.

Using methanol the effect of solvent replacement on the pore structure was also studied.

It was concluded that the use of solvent replacement procedure preserved the original pore structure of hydrated cement paste since the calculated and the measured bulk densities of the different W / C ratio pastes were found to be in excellent agreement.

Capillary condensation analysis was used to estimate the volume of capillary pores smaller than 4 nm diameter for the 0.6 and 0.75 W / C ratio pastes.

The 0.4 W / C ratio paste had very small pore sizes which could not be characterized by capillary condensation analysis.

The volume of pores smaller than 4 nm was estimated from volume - thickness (V-t) analysis.

For the three systems investigated, the volume of pores greater than 4 nm was obtained by MIP.

For solvent-replaced pastes, which showed capillary condensation according to V-t analysis, excellent agreement was obtained between the nitrogen sorption and MIP techniques in the 4 nm to 30 nm pore diameter range.