Determining the air void efficiency of fresh concrete mixtures with the Sequential air method

Abstract

The Sequential Air Method (SAM), AASHTO TP 118, is the only test that can quantify the air void volume and spacing in fresh concrete but using the results to design a concrete mixture can be challenging. This work introduces a new tool that uses the outputs from the SAM to determine how different ingredients or changes to the environment impact the volume and spacing of the air void system. This tool is known as the Efficiency Chart. The Efficiency Chart can help producers create more reliable and consistent air void systems that also meet the suggested freeze thaw requirements. The Efficiency Chart is made by using 227 diverse concrete mixtures to establish an upper and lower bound of performance. To show the usefulness of this method several examples are presented to show how different admixtures and cements impact the air void systems. Agreement is shown between the predictions of the Efficiency Chart and the results from a hardened air void analysis (ASTM C457). Because the SAM can evaluate fresh concrete, the concrete industry can use the Efficiency Chart to help design and troubleshoot the air void systems in their concrete mixtures.