Entrained air bubbles in concrete improve the freeze–thaw resistance by alleviating stresses caused by freezing water within the microstructure. It is necessary to achieve a uniform distribution of entrained air bubbles in the paste to achieve optimal freeze–thaw performance. The technique of measuring the air-void system parameters in hardened concrete is specified by ASTM C457/C457M-12. In this standard testing procedure, the freeze–thaw parameters of interest are determined by optically observing and measuring the traversal lengths of air voids, paste, and aggregate particles along straight lines across the polished surface of the concrete specimen. ASTM C457/C457M-12 has been criticized as time-consuming and expensive, and so there has been a concerted effort by the research community to develop improved methods. Automated methods that use digital images to measure freeze–thaw parameters exist, but they require operator-selected threshold levels and significant sample preparation time and labor. To address these shortcomings, this paper presents an automated method to measure freeze–thaw parameters using a high-resolution flatbed scanner, automated image segmentation, and short sample preparation time and labor. Polished concrete surfaces are treated with phenolphthalein and a florescent chalk powder to distinguish phases of interest. The surfaces are scanned using a flatbed scanner, and spectral–spatial analysis is used to identify the individual phases of aggregates, paste, and air voids. The ternary images are used to measure parameters of the air-void system. To validate the rigor of this automated method, six groups of concrete specimens provided by a commercial laboratory were tested using the proposed automated method and manual ASTM C457/C457M-12. This comparison was conducted in a “blind” fashion, so as to avoid potential biases. A fair agreement is found for normal concrete specimens, but not for concrete containing lightweight aggregates.

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