Stability and Quality of Air Void Systems in Concretes with Superplasticizers

Abstract

This study examines the effects of combining different polycarboxylate superplasticizers with different air entraining agents in modern concrete. A novel testing method was invented for analyze the changes over time in the mixtures as well as the stability of the air void system produced. Data collected included the slump, the unit weight, the fresh air content, the hardened air content, the spacing factor, the specific surface area, the rapid freeze thaw durability, and the modified fresh air content. All tests performed followed ASTM standards except for the modified air content test, which was contrived for this study. The results of the study indicated that some polycarboxylates will coarsen the air void system and cause stability issues. From the raw hardened air content data, the number of void chords smaller than 200 microns was calculated. This value proved a strong indication of the quality of the air system in the concrete. This metric for evaluating the air void system has not been reported in the past.