The influence of the addition of three commercially available superplasticizers employed for maximising the solid loading of very high strength Portland cement pastes has been investigated. Cement pastes were prepared from deionized water and a commercially manufactured Portland cement (Ultracem 52.5 R by Italcementi S.p.A., Bergamo, Italy). Cement and water were mixed with a vane stirred according to ASTM Standard C305. The 0.38 to 0.44 water/cement ratio range was investigated. The three superplasticizers employed (produced by RuredilS.p.A., S. Donato Milanese (Mi), Italy) are based on mixtures of synthetic polyfunctional polymers (Fluiment 40), on highly branched polymers containing specific functional groups (Fluiment SAE 25), and on polycyclic copolymers with modified structures, carrying hydroxylated side chains (Concretan RX), respectively. Rheological tests were performed at 25°C by using the rate controlled coaxial cylinder viscosimeter Rotovisko-Haake 20, system M5-osc., measuring device MV2P with serrated surfaces. The tests were carried out under continuous flow conditions. The results of this study were compared with those obtained in a previous article for an Ordinary Portland Cement paste.
