The influence of the addition of three commercially available superplasticizers employed for maximising the solid loading of Portland cement pastes has been investigated. Cement pastes were prepared form deionized water and a commercial ordinary Portland cement 32.5 R. Cement and water were mixed with a vane stiffer according to ASTM Standard C305. The water/cement ratio was kept fixed to 0.32. The superplasticizers tested 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). Rheological tests were performed at 25°C with the rate controlled coaial cylinder viscometer Rotovisko Haake 20, system M5-osc., measuring device MV2P with serrated surfaces. The tests were performed under both continuous and oscillatory flow conditions.
