Rapid Methods of Distinguishing Plasticizer From Superplasticizer and Assessing Superplasticizer Dosage


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Title: Rapid Methods of Distinguishing Plasticizer From Superplasticizer and Assessing Superplasticizer Dosage

Author(s): A. Verhasselt and J. Pairon

Publication: Special Publication

Volume: 119


Appears on pages(s): 133-156

Keywords: admixtures; compactibility; compositions; deflocculating; dosage; effectiveness; mortars (material); plasticizers; tests; Materials Research

Date: 9/1/1989

Except for degree of effectiveness, plasticizers and superplasticizers have very similar effects on the workability of hydraulic mixtures. In a microscopic scale, however, their action clearly differs by the effective deflocculation and the high dispersion of the cement particles obtained with superplasticizers. This behavior was the basis of development of two test procedures. The first one makes it possible to discriminate between both types of admixture. Furthermore, it reveals possible specific interactions with the cement used and makes it possible to assess the period of activity of a superplasticizer. The second procedure allows easy and quick assessment of the minimum active dosage required of a superplasticizer for a given cement. Though often higher than the percentages recommended by the manufacturers, the values agree well with those obtained by a vibratory compaction test on cement mortar. This test also allows a quick assessment of the relative effectiveness of various superplasticizers. From a study on 17 admixtures and two cements (one portland and one with granulated slag), it appeared that: an admixture supplied as a plasticizer may actually be a superplasticizer; an admixture may behave as a plasticizer or as a superplasticizer according to the nature of the cement; and the period of activity of the superplasticizers was generally longer with the slag cement.