Title: The Influence of Temperature on the Rheological Properties of Superplasticized Cement Pastes
Author(s): Carmel Jolicoeur, Jeff Sharman, Nathalie Otis,
Andree Lebel, Marc-Andre Simard and Monique Page
Publication: Symposium Paper
Appears on pages(s): 379-406
Keywords: Adsorption; cements; rheological propertis; silica fume; superplasticizers
The variation in rheological properties of normal portland cement type-10 and blended silica fume (SF) cement pastes was investigated as a function of temperature (0-40°C) in order to elucidate changes in concrete workability with ambient temperature. The rheological parameters measured included the Kantro mini-slump (spreading areas, S) and the dynamic viscosity (r> at various shear rates as a function of superplasticizer concentration (sodium polynaphthalene sulfonate, PNS). To interpret the changes in fluidity of the cement pastes, the concentration of the superplasticizer in the solution phase was monitored as a function of time measurements also measured of the earlv cement hydration rate (0- 3 hrs) in the pastes were in some cases. (O-2 hrs); calorimetric The variations observed in paste fluidity (S, or l/q) at a given PNS dosage exhibit significant non-linear variations with temperature; the rate of change of S and l/q with time (i.e. slump loss rate) are also found to be non-linear, usually with a maximum value in the interval 5-20°C. The non-linear effects are more pronounced with the SF cement than with the type-10 cement. The observations are interpreted tentatively on the basis of coupled physico-chemical effects involving PNS adsorption on cement and on silica, and the influence of PNS on the early hydration rate.