Cement/Superplasticizer/Air-Entraining Agent Compatibility

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Title: Cement/Superplasticizer/Air-Entraining Agent Compatibility

Author(s): M. Baalbaki and P. C. Aitcin

Publication: Special Publication

Volume: 148

Issue:

Appears on pages(s): 47-62

Keywords: air-entrained concrete; air-entraining agents; cements; compatibility methods; freeze-thaw durability; plasticizers; scaling; slump; superplasticizers; Materials Research

Date: 9/1/1994

Abstract:
It is well known that to successfully pass ASTM C 666 (Procedure A) for rapid freeze-thaw resistance, normal strength concrete must contain an adequate amount of entrained air composed of minute air bubbles with the right spacing factor. As concrete slump is increasingly restored at the jobsite using superplasticizer instead of retempering with water, it is essential that slump increase does not alter the total air content and air-void system if the concrete is to be frost-resistant. Since mixed results have been reported when superplasticizer is added to air-entrained concrete at the jobsite, a research program was undertaken to study the compatibility between three air-entraining agents, four water reducers, and one polynaphthalene sulfonate superplasticizer currently used in Eastern Canada. Experimental results conducted on 12 different combinations of admixtures with a Type 10 (ASTM Type I) portland cement show that the addition of superplasticizer nearly always increased the air content without changing the bubble spacing. The only case in which the air bubble spacing was significantly altered was when the air content of the concrete was lower than 4.5 percent 70 min after batching. In this case, the total air content decreased after the introduction of the superplasticizer, while the spacing factor increased significantly. A second Type 10 cement was used to duplicate these results. No significant difference was found between the results of the two sets of experiments.