Evolution of Various States of Water in Blended Cementitious Materials

Abstract

Low field NMR, as a nondestructure and noninvasive method was employed to study the evolution of various states of water in blended cementious materials added with fly ash during hydration from 1 day to 100 days. The relative content of water held in series of pores in cement matrix, e.g. capillary pore, mesopore and gel pore, was determined based on the quantitative relationship between transverse relaxation time, T2, and pore dimension. The results indicated that the relative content of chemically bound water was higher at long-term cure of 100 days compared with the neat cement paste. The water distributed in various pores was also influenced by the pozzolanic reactions between fly ash and calcium hydroxide. The gel water and mesopore water increased dramatically during the short-term age of 1 to 7 days in blended matrix, but then decreased gradually after 28 days, unlike that in pure cement paste. Due to the lower hydration degree in blended matrix, there was still amount of capillary water residual in paste to supply for the further hydration of fly ash.