Influence of Cross-Linked and NSF Superplasticizer on the Flow Properties of Blended Cements


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Title: Influence of Cross-Linked and NSF Superplasticizer on the Flow Properties of Blended Cements

Author(s): T. Sone, S. L. Sarkar, and H. Uchikawa

Publication: Special Publication

Volume: 148


Appears on pages(s): 153-176

Keywords: admixtures; blended cements; flowability; slump; superplasticizers; viscosity; Materials Research

Date: 9/1/1994

The corporate use of mineral admixtures, such as slag, silica fume, fly ash, and superplasticizer, in concrete is steadily rising for reasons of economy, enhanced strength, low heat generation, increased durability, and better rheological control. This study reports results of the influence of a cross-linked and NSF type of superplasticizer on the flow properties of blended cements. The cross-linked superplasticizer was comprised of polycarboxylic ether and cross-linked polymer, whereas the NSF type was a modified lignin, alkysulfonate, and polymer. In view of the difference in their molecular structures, their effect was studied on two types of cement: a normal portland cement and a moderate heat portland cement (belite-rich, low in C 3A), to which different proportions of slag, silica fume, and Class C and F fly ash were added to simulate binary and ternary blended cement compositions. Following a detailed chemical and mineralogical characterization of these blending components, the slump flow of 25 mortar blends were tested at a sand-binder ratio of 1.5, with the superplasticizer dosage varying from 2.5 to 3 percent by weight of cement. The water-binder ratio of these mixes ranged from 0.31 to 0.35. Marked differences in flow characteristics (determined by different methods) were recorded as a function of the cement type, blending component, and superplasticizer composition. Viscometric measurements made on the corresponding cement paste mixtures using a rheometer also exhibit pronounced differences in terms of their apparent viscosity. The possible superplasticizer interactions that occur in these blended cementitious systems are discussed. This study reiterates the cement-superplasticizer compatibility factor currently under intense discussion among researchers.