Novel methods of processing cement gel to examine and control microstructure and properties

Abstract

The microstructure of the gel produced by hydrating cement is sensitive to the manner in which the original pore water is removed. Exchange of the pore water with a miscible, low surface-tension fluid by a process of counter-diffusion is examined. Diffusion rates in the hydrated cement can be assessed from the kinetics of the exchange process. Evaporation of the low surface-tension fluid from the pores caused less alteration to the microstructure than direct removal of the original pore water. The sensitivity of the microstructure of hydrated cement to normal environmental drying is industrially significant because it is associated with increases in diffusion rates that could affect the durability of concrete. Drying lowered the correlation between diffusion rate and compressive strength. Possible methods of processing the cement gel to make it more resistant to the disruptive effects of drying are discussed.