Title: Mixing Procedure Parameters Affecting Air Entrainment in Concrete

Author(s): Marina Licht, Ida Ros, Roberta Magarotto

Publication: Symposium Paper

Volume: 354

Issue:

Appears on pages(s): 273-286

Keywords: air-entrained concrete; air-entraining agents; air void distribution; DoE, mixing procedure, reactivation potential

DOI: 10.14359/51736081

Date: 7/1/2022

Abstract:
Air-entraining agents have had years of success in improving resistance to freezing and thawing damage (due to both internal distress and salt scaling). However, this success has not come without some troubles as even today concrete producers wrestle with controlling air content in concrete. As well-known and reported in literature, the ability to consistently obtain target air-void systems in concrete is not trivial, and changes in raw materials, processing, or construction methods may significantly impact air entrainment. The present study investigates how the mixing procedure of concrete can affect air content and air void distribution. In addition, chemical parameters like air-entraining agent (AEA) and defoamer (DF) chemistries are examined. Mixing procedure parameters as mixing time and addition of the air entrainer before or after the defoamer-containing superplasticizer impact air stability and quality in a different way depending on the AEA type and on the interaction between the AEA and the DF. Mortar samples produced by different mixing procedures and mixing times with two different AEA and defoamer chemistries were tested. Air void diameter distribution of mortar samples was measured at fresh stage with an air-void analyzer (AVA). The interaction effects of the mixing procedure with the AEA and DF chemistries were quantified by the Design of Experiment (DoE).