Title:
Studies on Hydration in High-Volume Fly Ash Concrete Binders
Author(s):
Linhua Jiang, Baoyu Lin, and Yuebo Cai
Publication:
Materials Journal
Volume:
96
Issue:
6
Appears on pages(s):
703-706
Keywords:
admixtures; binders (materials); fly ash; hydration; microstructure; polymerization.
DOI:
10.14359/798
Date:
11/1/1999
Abstract:
Pastes made with different fly ash contents, water-cementitious ratios (w/cm), and admixtures were tested for up to 90 days. Strength development, thermal analysis, silicate polymerization analysis, pore structure analysis, x-ray diffraction analysis, and scanning electron microscopy were employed to study the hydration progress, hydration product, and microstructure of the pastes. It is determined that admixtures affect the progress of hydration, and activator admixtures can accelerate the hydration of high-volume fly ash (HVFA) concrete binders. The total porosity increases with increasing fly ash content and w/cm, and decreases with increasing age. The presence of fly ash can improve the pore size distribution. The fly ash in HVFA systems cannot be fully hydrated. The changes of (SiO4)4- polymerization degree behave irregularly during the hydration of HVFA systems. The contents of monomer and dimer in fly ash are very low, and the activity of fly ash is low. It is suggested that the fly ash content in HVFA concrete should be lower than 70%.