Fluidizing efficiency of comb-like superplasticizers: The effect of the anionic function, the side chain length and the grafting degree

• Published in: Cement and concrete research 2015-05, Vol.71, p.115-123
• Main Authors: Dalas, Florent, Pourchet, Sylvie, Nonat, André, Rinaldi, David, Sabio, Serge, Mosquet, Martin
• Format: Article
• Language: English
• Subjects: Admixture (D); Adsorption; Adsorption (C); CaCO3 (D); Carboxylates; Cements; Fluidizing; Grafting; Mathematical models; Polymers (D); Rheology (A); Superplasticizers; Viscosity
• ISSN: 0008-8846; 1873-3948
• DOI: 10.1016/j.cemconres.2015.02.001

Superplasticizers and especially polycarboxylate grafted polyethylene oxide (PCE) demonstrated their efficiency to fluidify concrete. The aim of this work is to investigate the evolution of the fluidity as a function of adsorption in a sulfated solution with a wide variety of comb-like superplasticizers and at incomplete adsorption rate. Polymers with various side chain lengths, grafting ratios and also with modified anionic functions (carboxylate, dicarboxylate and phosphate) were synthesized. Inert calcite suspensions were used to mimic early age cementitious materials avoiding the cement hydration. Models of polymer conformation and yield stress prediction have been tested. But the most appropriate parameter which captures the fluidity/adsorption relationship is the mass of adsorbed polymer. A unique relationship “log(yield stress) vs. adsorbed mass of PCE” has been highlighted whatever the classical carboxylate PCE structure. The modification of the anionic function does not enhance the fluidizing efficiency. Each PCE has roughly the same fluidizing efficiency when it manages to adsorb in these ionic conditions.