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Edition:Final report; Nov. 2005-Dec. 2007.
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Abstract:The two main test methods that measure the air content in plastic concrete are the pressure method and the volumetric
or roll-a-meter method. Although these methods report the total air in the concrete, they do not distinguish between
entrained air and entrapped air or the quality of the air void system. The quality of the air void system consists of the
content, distribution, and size of the air bubbles in the concrete matrix. In order to analyze the quality of the air void
system, a petrographic analysis is required on the hardened concrete. The downside of this procedure is that it requires
analysis of hardened concrete under a microscope which is time consuming, expensive, and results are determined well
after placement of the concrete. The air void analyzer (AVA) is a new device developed as an alternative to the
petrographic method that promises to provide air void system properties in a more timely matter while the concrete is
still in the plastic stage.
The intent of this research was to first, evaluate the air void analyzer and compare results with the petrographic
method to verify its results. Secondly, it was to correlate the use of various types of water reducing admixtures
(WRA) with various types of air entraining admixtures (AEA) into a generalized declaration that would state
which WRA and AEA is good at developing a quality air void system in concrete. In the initial course of this
investigation, the AVA demonstrated it was incapable of reliably reproducing results from the same batch of
concrete about 60 percent of the time. It was decided to end this study. This report presents the study findings.
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