Determining the carbonation depth is of paramount importance in assessing the durability of cementitious materials as the carbonation process alters their near-surface physicochemical properties. This paper introduces a novel quantitative ultrasound (QUS) technique capable of nondestructively identifying the carbonation depth, regardless of the tortuosity of the carbonation front. A 2.5 MHz phased array transducer was employed to construct beamformed radio frequency images and measure two microstructure-dependent parameters – spectral slope (SS) and spectral intercept (SI) – based on backscatter and attenuation coefficients. The change in obtained SS and SI were then visualized as QUS images, which displayed the geometry of the carbonation front, correlating with images constructed using a phenolphthalein solution (1.6 mm difference in depth). Mineral compositions and porosities were analyzed to account for microstructural changes in each layer. This study opens an opportunity for nondestructive detection of carbonation depth, overcoming the limitations in conventional methods or regression-based approaches.

中文翻译：

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碳化深度可以无损测量吗？水泥浆体高频定量超声成像

确定碳化深度对于评估水泥材料的耐久性至关重要，因为碳化过程会改变其近表面的物理化学性质。本文介绍了一种新颖的定量超声（QUS）技术，无论碳化前沿的曲折程度如何，都能够无损地识别碳化深度。采用 2.5 MHz 相控阵换能器构建波束形成的射频图像，并根据反向散射和衰减系数测量两个与微观结构相关的参数——光谱斜率 (SS) 和光谱截距 (SI)。然后将获得的 SS 和 SI 的变化可视化为 QUS 图像，该图像显示碳化前沿的几何形状，与使用酚酞溶液构建的图像相关（深度差异为 1.6 毫米）。分析矿物成分和孔隙率，以解释每层的微观结构变化。这项研究为无损检测碳化深度提供了机会，克服了传统方法或基于回归的方法的局限性。