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A
.gov website belongs to an official
government organization in the United States.
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Example images of FP groups (a–d), FN groups (e–h) and their crack probabilities (a–d): (a) crack-shaped contaminants; (b) overlaid cement paste; (c) continuously distributed concrete pores; and (d) edge of linear-shaped construction material; (e) crack hidden behind object; (f) crack having straight line; (g) crack obscured by dark surface; and (h) crack on the corner of detecting window.
