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Image Analysis of PCC and AC Pavements Using Sem Images
The major objective of this work was to evaluate the potential of image analysis for characterizing air voids in Portland Cement Concrete (PCC), voids and constituents of Asphalt Concrete (AC) and aggregate gradation in AC. Images for analysis were obtained from a scanning electron microscope (SEM). Sample preparation techniques are presented that enhance signal differences so that backscattered electron (BSE) imaging, which is sensitive to atomic number changes, can be effectively employed. Work with PCC and AC pavement core samples has shown that the low vacuum scanning electron microscope (LVSEM) is better suited towards rapid analyses. The conventional high vacuum SEM can also be used for AC and PCC analyses but some distortion within the sample matrix will occur. Images with improved resolution can be obtained from SEM BSE micrographs. In a BSE image, voids filled with barium sulfate/resin yield excellent contrast in both PCC and AC. There is a good correlation between percent of air by image analysis and linear traverse.
The Effect of Deicing Salt on Aggregate Durability
Since 1962, the Iowa DOT has been using the methods of rapid freezing in air and thawing in water to evaluate coarse aggregate durability in concrete. Earlier research had shown that the aggregate pore system was a major factor in susceptibility to D-cracking rapid deterioration. There are cases in which service records indicate that on heavily salted primary roads, concrete containing certain aggregates show rapid deterioration while the same aggregates show relatively good performance on secondary roads with limited use of deicing salt. A fivecycle salt treatment of the coarse aggregate before durability testing has yielded durability factors that correlate with aggregate service records o...
Inside Magazine
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Concrete Research
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Salary Book
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Iowa Pore Index Test
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