Title:
Rheology and Setting of Alkali-Activated Slag Pastes and Mortars: Effect of Organic Admixture
Author(s):
Marta Palacios, Phillip F. G. Banfill, and Francisca Puertas
Publication:
Materials Journal
Volume:
105
Issue:
2
Appears on pages(s):
140-148
Keywords:
alkali-activated cement; cement paste; mortar; rheology; setting; shrinkage.
DOI:
10.14359/19754
Date:
3/1/2008
Abstract:
The rheology of waterglass-(Na2O·nSiO2·mH2O) and NaOH-activated slag pastes and mortars depends on the nature of the alkaline activator used: in waterglass-activated slag pastes and mortars, the extensive structural breakdown under shear makes the Herschel-Bulkley model a better fit to the down ramp of the flow curve, whereas NaOH-activated pastes and mortars, such as portland-cement pastes and mortars, behaved like Bingham fluids. Admixtures were unable to reduce the yield stress of waterglassactivated slag pastes, but the inclusion of a naphthalene derivative admixture in NaOH-activated slag pastes reduced the yield stress by 80%. The problem of undesirably short setting times for waterglass-activated slag mortars and concretes could be overcome by an extended mixing time, giving an initial set of nearly 3 hours.