{'fraction_non_alphanumeric': 0.033404406538734895, 'fraction_numerical': 0.007107320540156361, 'mean_word_length': 4.565217391304348, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Subsurface characterization of moisture content and water-to-cement ratio of concrete specimens using remote synthetic aperture radar imaging

Abstract. In civil engineering, determining the subsurface moisture content and the water-to-cement (w  /  c) ratio of concrete structures in the field is a challenging task. Moisture content of concrete structures regards the cement hydration level and short-term strength development of concrete, as well as the phase-distribution (solid, gaseous, and liquid) inside concrete and its long-term durability. We describe a microwave nondestructive evaluation technique using noncontact/nonintrusive synthetic aperture radar (SAR) imaging to estimate both the w  /  c ratio and subsurface moisture content of concrete panels. Concrete panels made of three w  /  c ratios (0.4, 0.5, and 0.55) were air dried for ∼3 months and scanned by a laboratory 10-GHz SAR imaging system. From this research, we found that SAR imaging can capture the moisture content variation and its spatial distribution. A parameter of SAR images, the critical contour area, is identified and proposed for estimating subsurface moisture content and the w  /  c ratio of concrete panels. At a given w  /  c ratio, the critical contour area increases with the increase of moisture content. At a given moisture content, the critical contour area decreases with the increase of the w  /  c ratio.