Ultra-high performance concrete (UHPC) is a versatile and highly durable form of concrete that has a high tensile and flexural strength.&nbsp; The increased tensile and flexural strength is, in part, the result of thin, steel fibers within the mixture. When fabricating UHPC, the concentration and orientation of the steel fibers should be uniform across the structure. Improperly placed steel fibers can have a debilitating effect on material strength and cause unexpected structural failure. Yet, identifying the concentration and orientation of these fibers remains a challenge. Fortunately, these steel fibers are ferromagnetic, which means they are highly attracted in the presence of a magnetic field. In contrast, UHPC is paramagnetic, which means that it is not strongly attracted in the presence of a magnetic field.&nbsp; This ferromagnetic property of steel fibers makes it possible to distinguish them from the other components that make up the concrete through magnetic sensing techniques.To exploit this property, we designed an electromagnetic device that is made up of 320 turns of American wire gauge 25 wrapped around an N87 ferrite core to detect the volume and orientation of steel fibers in UHPC. Whenever a current is passed through this coil of wire, a magnetic field is formed around that wire.&nbsp; This device detects the changing inductance of the electromagnetic device in the presence of steel fibers. Our experimental setup consists of various UHPC samples consisting of different fiber percentages, ranging from 1 to 3%. We further tested our work using several full-scale UHPC structures, including H-piles, I-beams, octagonal piles, and square piles. We also validate our results using a CT scanner to assess cores taken from a subset of the structures. Our results show that we can detect fiber percentages and orientation using our electromagnetic device as well as a close match between the fiber percentage results from the lab with the fiber percentages measured from the field specimens.&nbsp;Acknowledgement 
The authors will like to thank the Florida Department of Transportation (FDOT), for providing the funding for this project under the task work order # BDV31 TWO 977-105.

An Electromagnetic Nondestructive Device for Ultra-High Performance Concrete (Uhpc)

Paper Proceedings: https://asmedigitalcollection.asme.org/qnde/QNDE2021/volume/85529

ASME 2021 48th Annual Review of Progress in Quantitative Nondestructive Evaluation (QNDE2021)

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