United States Department of Transportation
i
Development of Protocol to Maintain Winter Mobility of Different Classes of Pervious Concrete Pavement Based on Porosity
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2019-12-15
[PDF-3.46 MB]
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Edition:Final report (09/01/2017-12/31/2019)
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Abstract:The main focus of this study was to develop an image-based method to characterize the porosity of in-situ pervious concrete (PC), so this feature can be correlated with ice formation and winter maintenance operations of the pavement. First, a surface imaging-based porosity characterization method was investigated. A total of 27 PC slabs cast at three targeted porosity levels—15 percent, 25 percent, and 35 percent--were used. Images of the top and bottom surfaces of the slabs were used in thresholding techniques, in which the images were binarized and the area of the voids were obtained. The image-based porosity was calculated as the ratio of the area of voids to the total surface area of each slab. The image-based porosity was correlated with the porosity of the PC measured in accordance with ASTM C1754 by submersion. For validation, the distribution of the porosity along the depth of PC cores extracted from the slabs was quantified from images taken by X-ray computed tomography (CT). Analysis of these images revealed that the distribution of pores along the depth were significantly different at intermediate depths than that at the top and bottom 0.5-inch depths because of compaction. Therefore, the developed surface image-based method did not provide a representative porosity value for the full PC layer. More surface imaging, in parallel with X-ray CT scans, are required to develop a correlation between the porosity of the surface layer and overall porosity. Finally, the Gibbs-Thompson equation, a thermodynamic-based model developed in past studies, was recommended to determine the critical temperature at which ice formation initiates inside PC pores. The proposed image-based porosity characterization method and the Gibbs-Thompson equation can be used as a decision support tool for transportation authorities to identify the time of ice formation in PC pavements in order to apply timely winter maintenance treatments.
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