Comparison of methods for arresting hydration of cement

Arresting of cement hydration, followed by drying, is necessary to prepare samples for many techniques of microstructural analysis. This paper reviews the effects on microstructure and composition of cement paste caused by the most common drying techniques, including direct drying (oven, microwave, D-drying, P-drying, and freeze drying) and solvent exchange methods. Supercritical drying is proposed as a method that could effectively preserve the cement microstructure, but which has not been applied to cementitious materials. Experiments are reported that systematically quantify the effects of drying from several solvents, freeze drying, and direct drying of young paste. Freeze drying is an effective drying method to prepare samples for chemical analysis, but it might change the microstructure. Isopropanol exchange followed by ambient drying is the best known method for preserving the microstructure with minimal effect on the composition of cement.