In the present work, the influence of the addition of some dispersing agents employed for maximizing the solid loading of calcium carbonate concentrated suspensions was investigated. Three commercial deflocculants were used:a sodium salt of a benzenedisulfonic acid (Tiron), a sodium polyphosphate, and an aurintricarboxylic acid, triammonium salt (Aluminon). Calcium carbonate aqueous suspensions were prepared at various solid volume fractions (0.270 to 0.382). Rheological tests were carried out at 25°C by using the rate-controlled coaxial cylinder viscometer Rotovisko-Haake 20, system M5-oscillatory, measuring device SV2P with serrated surfaces. The tests were performed under both continuous and oscillatory flow conditions. The application of rheological techniques permitted highly accurate evaluation of the optimum dosage of the deflocculants, i.e., the critical concentration at which the maximum reduction in viscosity is detected. Generally, Aluminon and sodium polyphosphate behaved as the best dispersing agents for the calcite suspensions studied, i.e., they showed their optimum dosage at a concentration lower than that of Tiron and provided low viscosity values for the entire concentration range explored.
