Concrete Pavement MDA: Evaluation of Foam Drainage Test to Measure Air Void Stability in Concrete
Iowa State University’s National Concrete Pavement Technology Center (CPTech Center) has published the report, “Concrete Pavement MDA: Evaluation of Foam Drainage Test to Measure Air Void Stability in Concrete”. ISCP Board of Directors Member, Peter Taylor, Associate Director National Concrete Pavement Technology Center, Iowa State University, is the Principal Investigator and co-author. The report was sponsored by the Federal Highway Administration (FHWA) and nine U.S. Departments of Transportation (US-DOTs).
The total air content of a mixture is normally measured before concrete is placed into its final position and consolidated. This practice is acceptable only if the air void system is stable. A test that assesses the stability of air void systems was reported by Cross et al. (2000), and reviewed by Taylor et al. (2006). While the test showed promise, little correlation with field performance was available and it has not found much traction.
The aim of the work reported in this document was to continue to evaluate the test using paste systems in use today. The stability of air bubbles in fresh concrete can have a profound influence of the potential durability of the system, because excessive losses during placement and consolidation can compromise the ability of the mixture to resist freezing and thawing. The stability of air void systems developed by some air entraining admixtures (AEAs) could be affected by the presence of some polycarboxylate-based water reducing admixtures (WRAs). The foam drainage test provides a means of measuring the potential stability of air bubbles in a paste. A barrier to acceptance of the test was that there was little investigation of the correlation with field performance.
The work reported here was a limited exercise seeking to observe the stability of a range of currently available AEA/WRA combinations in the foam drainage test; then, to take the best and the worst and observe their stabilities on concrete mixtures in the lab. Based on the data collected, the foam drainage test appears to identify stable combinations of AEAs and some polycarboxylate-based WRAs.
To read the entire report, please download the PDF “Concrete Pavement MDA: Evaluation of Foam Drainage Test to Measure Air Void Stability in Concrete“.