A Summary of Important Characteristics of Cement and Superplasticizers

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Title: A Summary of Important Characteristics of Cement and Superplasticizers

Author(s): K. Yamada

Publication: Special Publication

Volume: 262

Issue:

Appears on pages(s): 85-96

Keywords: adsorption; particle size; polycarboxylate; poly-naphthalene sulfonate; sulfate; superplasticizers; working mechanism.

Date: 10/1/2009

Abstract:
Significant numbers of studies on the working mechanisms of superplasticizers have elucidated many important characteristics of cement. However, because of the lack of general reviews, similar research activities tend to be repeated. Therefore, it is worthy to summarize a research on this issue based on the authors' experiences, including some unpublished miscellaneous but interesting data, irrespective of its bias or imperfection. The first point is the effect of sulfate ions on the adsorption and dispersing performances of poly- naphthalene sulfonates (NS) and polycarboxylate-type (PC) superplasticizers. With the addition of cations that make insoluble salts with sulfate ion, the dispersing performances of both NS and PC are increased. This emphasizes the importance of absorption. The second point is the effect of carboxylic groups on the initial hydration. A PC with too many carboxylic groups accelerates the initial hydration of cement. This acceleration can be controlled by the addition of soluble sulfate salts. In this case, sulfate ions increase the dispersing performance of PC. The last point is the importance of fine particles in ultra low water-cement ratio (w/c) range. There is a suitable range of particle size around 1 pm.