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A Practical Model for the Interactions Between Hydrating Portland Cements and Poly‐β‐Naphthalene Sulfonate Condensate Superplasticizers
Author(s) -
Nakajima Yutaka,
Goto Takaharu,
Yamada Kazuo
Publication year - 2005
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1551-2916.2005.00206.x
Subject(s) - superplasticizer , dispersant , naphthalene , cement , adsorption , sulfonate , absorption (acoustics) , sorption , chemical engineering , chemistry , portland cement , materials science , composite material , mineralogy , dispersion (optics) , organic chemistry , sodium , optics , physics , engineering
The performance of poly‐β‐naphthalene sulfonate condensate superplasticizer (BNS) as a dispersant for cement in concrete is affected severely by slight differences in the characteristics of the cement. In order to be able to predict these effects, a model for estimating the fluidity of cement paste containing BNS is proposed. This model is based on an assumption that the fluidity of cement paste is proportional to the BNS adsorption amount per surface area of hydrated cement (Ad/Hy). BNS is known to show two types of sorption on hydrated cement: one is the bulk absorption into initial hydrates and the other one is the superficial adsorption onto hydrates. Only the superficially adsorbed BNS is expected to work as a dispersant. By assuming a competitive Langmuir‐type adsorption on hydrates between BNS and SO 4 2− , a simple method to estimate Ad/Hy is developed, with the concentrations of BNS and SO 4 2− as the only two independent parameters. The resulting estimates of Ad/Hy show a good correlation with paste flow and its change with elapsed time for a broad range of cements. The SO 4 2− concentration in the aqueous phase of the cement paste just after the beginning of the mixing is known to affect the performance of BNS as a dispersant. By using the proposed model to discriminate between the superficial adsorption and bulk absorption of BNS, this phenomenon is explained quantitatively.