Effect of Superplasticizers on the Workability of Concrete as Evident from Apparent Viscosity, Yield Stress and Zeta-Potential

Abstract

AbstractModem concrete technology projections indicate a great expansion in low-cost and time efficient construction. Mixture designers will likely be more concerned with the developments in concrete making materials. Among those is the effective use of chemical admixtures and superplasticizers which will lower the water to cement ratio but will still give a dense workable concrete. An investigation of the workability of fresh concrete and the effect of superplasticizers should, therefore, constitute an essential part of modem concrete durability studies.In this paper we report part of the work on rheological properties of fresh concrete. Various concrete samples covering a range of compositions that are commonly used for highway pavements are prepared. The proportioning parameters are: cement content, aggregate size, gradation and sphericity-roundness, and water and superplasticizer contents. The individual solid ingredients were characterized and the fresh concrete properties were assessed by the slump, two-point workability (Tattersall's) apparatus, air pressure and unit weight methods. The effects of superplasticizer on the apparent viscosity and yield stress of concrete are discussed and the relevance of the findings for field applications (handling of fresh concrete) are discussed. Also discussed are the implications for microstructural development.