The Filler Effect: The Influence of Filler Content and Surface Area on Cementitious Reaction Rates
Tandre Oey, Aditya Kumar, Jeffrey W. Bullard, Narayanan Neithalath, Gaurav Sant
Finely ground mineral powders are known to accelerate cement hydration rates. This "filler effect" has been attributed to the effects of dilution (w/c increase) when the cement content is reduced or to the provision of additional surface area by fine powders. The latter contribution (i.e., surface area increase) is speculated to provide additional sites for the nucleation of hydration products, which accelerates reactions. Through extensive experimentation and simulation this paper describes the influence of surface area and mineral type (i.e., quartz or limestone) on cement reaction rates. Simulations using a boundary nucleation and growth (BNG) model and a multiphase reaction ensemble (MRE) indicate that the extent of the acceleration is linked to the: (1) magnitude of surface area increase and (2a) capacity of the filler's surface to offer favorable nucleation sites for hydration products. Other simulations using a kinetic cellular automaton model (HydratiCA) suggest that accelerations are linked to: (2b) the interfacial properties of the filler which alters (increases or decreases) its tendency to serve as a nucleant and (3) the composition of the filler and the tendency for its ionic constituents to participate in ion exchange reactions with the calcium silicate hydrate product. The simulations are correlated with accelerations observed using isothermal calorimetry when fillers partially replace cement. The research correlates and unifies the fundamental parameters that drive the filler effect and provides a detailed mechanistic understanding of the influence of filler agents on cementitious reaction rates.
, Kumar, A.
, Bullard, J.
, Neithalath, N.
and Sant, G.
The Filler Effect: The Influence of Filler Content and Surface Area on Cementitious Reaction Rates, Journal of the American Ceramic Society, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=912151
(Accessed December 2, 2023)