SYMPOSIA PAPER Published: 01 January 2010

The Practical Application of a Flatbed Scanner for Air-Void Characterization of Hardened Concrete


Over the past 30 years, with the advent of computers and digital imaging, many automated systems have been introduced for the purpose of air-void characterization. The majority of the systems employs a contrast-enhancement procedure where a polished cross-section of concrete is darkened with paint, and white powder is forced into the depressions left by air-voids. The system described here follows the same approach and uses a flatbed scanner to collect a single digital image of the entire sample. For all of the systems based on contrast enhancement, the first step is to select a threshold level. Image pixels brighter than the threshold level represent air and image pixels darker than the threshold level represent non-air (i.e., paste or aggregate). Further digital processing steps may be employed but the initial selection of threshold level exerts a strong influence on whether a pixel in the final data set is classified as air or non-air. A systematic approach for threshold determination has been proposed based on an iterative procedure that compares automatically determined air-void parameters to manually determined air-void parameters from a set of training specimens. The calibration procedure finds a single optimum threshold level for the automated system that is to be used for all subsequent analyses. The approach was tested on a population of 88 specimens with manually determined air-void parameters, with the goal of determining an appropriate value for the number of training specimens.

Author Information

Peterson, Karl
Michigan Technological Univ., Houghton, MI
Sutter, Lawrence
Michigan Technological Univ., Houghton, MI
Radlinski, Mateusz
Exponent, Menlo Park, CA
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Developed by Committee: C09
Pages: 41–63
DOI: 10.1520/STP49082S
ISBN-EB: 978-0-8031-8423-7
ISBN-13: 978-0-8031-3419-5