Title:
Influence of Soluble Alkalies on the Production and Stability of the Air-Void System in Superplasticized and Nonsuperplasticized Concrete
Author(s):
Michel Pigeon, Patrick Plante, Richard Pleau, and Nemkumar Banthia
Publication:
Materials Journal
Volume:
89
Issue:
1
Appears on pages(s):
24-31
Keywords:
air-entrained concretes; alkalies; mixing; portland cements; solubility; stability; superplasticizers; Materials Research
DOI:
10.14359/1241
Date:
1/1/1992
Abstract:
Fifty-four different concrete mixtures were studied to investigate the influence of soluble alkalies on the production and stability of the air-void system in normal as well as superplasticized air-entrained concrete. Two normal portland cements, three air-entraining agents, and two types of superplasticizer were used. Sodium sulfate in the amount of 1 percent of the dry cement mass (calculated as Na 2O equivalent) was added to 18 mixtures, and sodium hydroxide (in the same amount) was added to 18 others. The air-void characteristics of the hardened concretes were determined on specimens of each mixture cast after three different periods of mixing and agitation: 10, 30, and 60 min. The test results show that the production of the air-void system (i.e., the value of the spacing factor in specimens cast after 10 min of mixing) is not significantly influenced by the amount of soluble alkalies, but that an increase in the amount of sulfate ions present generally tends to increase the initial value of the spacing factor. The stability of the air-void system (as measured by the variation of the value of the spacing factor with the time of casting of the specimens), however, was found to increase very significantly with the amount of soluble alkalies, particularly in superplasticized mixtures.