X-Ray Computed Tomography for Studying the Effect of Durability Testing on Aggregate Pore Characteristics
17 Pages Posted: 2 Apr 2022
X-Ray Computed Tomography (CT) can be utilized to visually inspect individual aggregate particles on a small scale and create 3D images that accurately represent the material structure. By scanning an aggregate particle, one is able to ascertain properties such as pore size, tortuosity, distribution, and connectivity. These pore characteristics are very relevant to the freeze-thaw resistance as freeze/thaw damage originates from the confinement of water in a particle’s pore and the expansion of water with temperature drops. The pore properties also change with time as the sample undergoes freeze/thaw cycles. In this paper, high-resolution X-ray CT scans were performed on six aggregate sources subjected to unconfined freeze/thaw and sodium sulfate soundness testing; to compare and contrast the effects of these tests on the damage and change in pore structure of individual aggregates. The scans were conducted at the Argonne National Laboratory’s Advanced Photon Source (APS), and the virgin aggregates were also scanned. High-resolution and three-dimensional images of the inside of these aggregates were obtained using a specialized software, including void spaces. Porosity analysis demonstrated that freeze/thaw and soundness tests significantly increased the connected pore space and induced cracks in the solid material. The method quantified and compared the percentage increase in porosity after the two durability tests, and no trend was found between the increase in pore space resulting from freeze/thaw and that induced by sodium sulfate soundness test. This paper thus proposes an approach to characterize aggregates, where the pore structure and distribution are correlated to aggregate behavior.
Keywords: X-ray computed tomography, Aggregates, Durability, Void Structure, Image Analysis, Connected Voids, Freeze/Thaw, Soundness Testing
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