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http://www.trb.org/Main/Blurbs/180248.aspx

Fast Reference‐free Crack Measurement (RACM) System in Transportation Infrastructures using Noncontact Ultrasound

According to a 2017 report by the American Society of Civil Engineers, the infrastructure of the United States requires a $2.0 trillion investment to return it to good condition by 2025. Distributed micro-cracking and delaminated damage in the transportation system’s concrete infrastructure has caused more deterioration by the cracks and more delamination by corrosion, adversely affecting the system components’ mechanical strength, stiffness and permeability. Although previous research identified that ultrasonic and other nondestructive approaches can characterize distributed damage content in inhomogeneous infrastructure, the methods are either insensitive to early stages (low crack volumes) of damage, not repeatable, or inconsistent. These methods have an inadequate contact system that cannot measure the damage quickly enough as they require a contact to the surface and a more sophisticated reference data system that can more readily respond to the nature of the heterogeneous aspects of the problem sites. This proposal offers a solution in the form of a reference‐free acoustic crack measurement (RACM) system. The RACM system offers in‐situ or absolute damage index values. The in‐situ monitoring system does not need any control or reference data to assess the infrastructure. The RACM is also a fully contactless damage assessment system. The deployment of inexpensive but high performance contactless (air‐coupled) ultrasonic sensors offers the potential to overcome some current limitations and to provide a pathway for automated rapid inspection of transportation infrastructures. This system will provide quantifiable cost and time effort benefits for better monitoring and better decision making, which will increase the infrastructure service life. The proposed RACM system’s most important contribution is cutting the remediation costs of transportation concrete infrastructure through a more efficient detection and analysis system.