Suspensions of two types of cements modified with different doses of melamine formaldehyde type of plasticizer were rheologically tested by an alternative method of centrifugation. The sorption of organic molecules on the cement particles was evaluated in order to verify the plasticizer efficiency. Regression analysis showed a considerable influence of the plasticizer's sorption on the rheological parameters of suspensions. POLYM. COMPOS., 34:1483–1488, 2013. © 2013 Society of Plastics Engineers