Title: Fluidizing Mechanism and Application of Polycarboxlate-Based Superplasticizers
Author(s): A.Ohta,T.Sugiyama and Y.Tanaka
Publication: Symposium Paper
Appears on pages(s): 359-378
Keywords: Concrete technology; dispersants; superplasticizers; tests
The significant increase in large high-rise concrete structures has dictated diverse requirements for concrete. Concrete technology has improved, widening the range of applications of this material. In this regard, the technology of polycarboxylate-based superplasticizers has made remarkable progress; a number of new superplasticizers have been developed and applied to big construction projects. To elucidate the fluidizing mechanism of superplasticizers in cement, we focused on the fact that the chemical structure of these superplasticizers changes in an alkali environment. We determined the absolute molecular weight of the superplasticizers using the light scattering method, measured the amount adsorbed, zeta potential, and nuclear magnetic resonance. Based on our finding pertaining to polycarboxylate-based superplasticizers, we discuss the fluidizing mechanism of cement compositions with relevance to dispersibility, dispersibility retention, and flowability. We refer to DLVO theory, steric repulsion effect theory, depletion effect theory, tribology effect, as well as the results of mortar and concrete tests. We also report on the applications at big projects, such as the anchorage of the Akashi Channel Bridge and the deep ground continuous wall of the Tokyo Trans-Bay Highway.