Details

Autor(en) / Beteiligte

• Ossetchkina, Ekaterina
• Chernoloz, Oleksiy
• Bromerchenkel, Lucas Herzog
• Karim, Mahzabin
• MacHale, Liam
• Montgomery, Amy
• Hu, Yuqi
• Peterson, Karl

Titel

Paste, aggregate, or air? That is the question

Ist Teil von

• Journal of microscopy (Oxford), 2024-05, Vol.294 (2), p.191-202

Ort / Verlag

England: Wiley Subscription Services, Inc

Erscheinungsjahr

2024

Link zum Volltext

Quelle

Wiley Online Library

Beschreibungen/Notizen

• The Ambassador Bridge between Detroit, Michigan, and Windsor, Ontario, has served for almost 100 years as North America's busiest international border crossing. But in 2025, the Ambassador will be replaced by the new Gordie Howe International Bridge. The Gordie Howe is a cable‐stayed bridge, with two massive 220 m tall concrete piers on opposite banks of the St. Claire River, a single clear span of 853 m, and 42 m of clearance over this busy waterway. To ensure durability in this harsh freeze‐thaw environment, air‐entrained concrete is specified throughout. And, to ensure the quality of air entrainment, the ASTM C 457 Procedure C, Contrast Enhanced Method is employed. While a similar automated microscopic approach has been in use for well over a decade according to EN 480‐11 Determination of air void characteristics in hardened concrete, this is the first large‐scale application of automated air void assessment in North American infrastructure. According to the ASTM Procedure C, the air void characteristics are determined through digital image processing, while the paste content may be determined by either mix design parameters, manual point count, or ‘other means’. Of these three options, point counting is used for Gordie Howe; but in parallel, during each point count, the digital image coordinates and phase identifications for each evaluated stop are recorded. This allows for training of a neural network, for automated determination of paste content, as demonstrated here. LAY DESCRIPTION The Ambassador Bridge, which connects Detroit, Michigan, to Windsor, Ontario, has been the most heavily used border crossing in North America for nearly a century. However, it is set to be replaced in 2025 by the new Gordie Howe International Bridge. This modern bridge will feature two tall concrete towers and a long span over the river, designed to withstand the freezing and thawing cycles that occur from the climate in the region. To ensure longevity, the concrete contains dispersed microscopic air bubbles (air‐entrained concrete) that help to dissipate pressures generated during freeze‐thaw. The size distribution and spatial distribution of these air bubbles are routinely checked by trained technicians according to standard procedures, a tedious and time‐consuming process. Artificial intelligence has the potential to streamline these measurements, and its utility is explored here, showing promise for making future evaluations quicker and more accurate.