Study on Freeze-Thaw Damage Features of Coal Gangue-Fly Ash-Lime Mixture Based on Computed Tomography Scan

Abstract

Considering the freeze-thaw damages of coal gangue-fly ash-lime (CG-FA-L) mixture road base, this paper applies the computed tomography (CT) scan to investigate the freeze-thaw damage features of the mixture. Several freeze-thaw tests were carried out to disclose the attenuation law of the frost-resistance coefficient of the mixture. The micro-defect propagation of the CG-FA-L was analyzed by comparing the gray level histograms of the CT images on each specimen before and after freeze-thaw cycles. The loss of cross-sectional area in each specimen was calculated quantitatively by image segmentation. The results show that the frost-resistance index attenuated linearly with the increase in the number of cycles; the defects induced by freeze-thaw cycles were mostly less than 15mm deep, and grew at an increasingly fast speed as the number of cycles surpassed 5; the micro-defect caused by freeze-thaw action mainly affected the depth between 15 and 35mm; under the freeze-thaw cycles, the micro-defects inside the mixture mostly appeared in the cementitious materials of the fly ash and lime; the CT technology was applied satisfactorily in the analysis on the freeze-thaw features of the CG-FA-L mixture.