The effect of superplasticizers on the centrifugal consolidation behaviour of magnesia suspensions has been studied. The superplasticizers adsorb onto the MgO surface and infer a steric repulsion that reduces the degree of flocculation. The density profiles of the particulate cakes have been measured and the maximum volume fraction of the consolidated particle network is related to the inter-particle force. The implications of this simple compression rheological method for evaluating the stabilizing mechanism of superplasticizers are discussed.