Title:
Flocculation Behavior of Cement Pastes
Containing Clays and Fly Ash
Author(s):
N. Tregger, H. Knai, and S.P. Shah
Publication:
Symposium Paper
Volume:
259
Issue:
Appears on pages(s):
139-150
Keywords:
clay; compressive rheology; flocculation; fly ash; green strength; volume
fraction
DOI:
10.14359/56542
Date:
2/1/2009
Abstract:
The fresh state of concrete is becoming increasingly important in furthering the types of applications in today’s construction world. Processing techniques that have resulted in new technologies such as self-consolidating concrete depend on the microstructural changes within the cement paste during the first hours after mixing and placing. These changes to the microstructure reflect flocculation between particles in suspension. The ability to modify this behavior allows control over the balance between flowability and shape-stability of concrete. This study uses a centrifuge method to determine the relationship between local volume fraction (volume fraction of the sediment region) and compressive yield stress within cement pastes. Based on this relationship, the effectiveness that different admixtures such as clays and fly ash have on the balance between flowability and shape-stability can be measured. Results are consistent with green strength tests performed on example concrete mixes derived from the cement paste mixes.