New insight of solvent-replacement-induced damage to pores of cement stone by comparison with 1H NMR relaxometry, mercury intrusion porosimetry, and nitrogen adsorption

Abstract

The consensus on the damage to pore structure of cement-based materials caused by solvent-displacement-drying method has yet not been achieved. This work explored the effect of replacing pore water with ethanol, methanol, isopropanol, cyclohexane and acetone on the pore parameters of hardened white cement paste by means of low field NMR, mercury intrusion porosimetry and nitrogen adsorption techniques, with direct-drying (oven-drying and vacuum-drying) as the control. The results show that the degree of damage to the pore structure after secondary-solvent-replacement is close to that of direct- drying in terms of porosity, total pore area, characteristic pore size and pore size distribution. The difference of pore parameters of samples dried by different solvent-displacement is caused by the physical properties of solvents and the reaction with hydration products. Furthermore, thermal analysis results have confirmed the reaction between acetone and hydration products to generate a dark brown substance. If the possible chemical reaction between organic solvents and hydration products is not considered, the pore structure of cement stone can be well protected by replacing pore water with methanol.