Air Contained in Superplasticized Concretes
Giampietro Tognon and Stefano Cangiano
Appears on pages(s):
air-entrained concretes; air entraining agents; air entrainment; bubbles;consistency tests; formaldehyde; fresh concretes; naphthalene; plasticizers;slump tests; vebe tests; water-cement ratio; water content; vibration; workability.
The air-entraining activity of superplasticizers based on sulfonated naph thalene formaldehyde condensates was studied in concretes made with different water-cement ratios. Results indicated that these admixtures cause air entrainment which is directly related to the workability of mixes. Nevertheless, the comparison with concretes containing an air-entraining agent showed that the air bubbles introduced by the super-plasticizers are not bound to the cement particles and are characterized by sizes two to four times as high as those due to an air-entraining agent. Also, when working with superplasticized self-leveling concretes, a vibrating, even if moderate, action is necessary to eliminate the entrained air that, because of its size, is not useful against frost action.