The reuse of steelmaking slag is a crucial step to protect the environment. However, steelmaking slag can cause road cracking when reused for road construction owing to the volumetric expansion of its free magnesia (f-MgO) content related to the hydration reaction. A method for rapidly determining the f-MgO content is not well established. The authors present a method for rapidly identifying and determining the f-MgO content of industrial steelmaking slag using a scanning microscopy-cathodoluminescence (SEM-CL) instrument. The colors of CL images and contrast of backscattered electron (BSE) images can be used to distinguish f-MgO from other minerals in the slag, such as MgO·Al₂O₃ spinel, merwinite, pseudowollastonite, and melilite by observing areas with dark gray in the BSE image contrast and no luminescence color in CL images at 420 to 680 nm wavelength. The f-MgO content can then be determined according to the areas of f-MgO identified in the BSE and CL images. In experiments, the BSE and CL images were acquired within 10 seconds. Thus, the proposed method can be used to rapidly determine the f-MgO content in industrial steelmaking slag.

炼钢渣的再利用是保护环境的关键步骤。然而，由于与水化反应相关的游离氧化镁（f-MgO）含量的体积膨胀，炼钢渣在重新用于道路建设时会导致道路开裂。快速测定 f-MgO 含量的方法尚未完善。作者提出了一种使用扫描显微镜-阴极发光 (SEM-CL) 仪器快速识别和测定工业炼钢渣中 f-MgO 含量的方法。CL 图像的颜色和背散射电子 (BSE) 图像的对比度可用于区分 f-MgO 与渣中的其他矿物，如 MgO·Al ₂ O ₃通过在 420 至 680 nm 波长下观察 BSE 图像对比度中的深灰色区域和 CL 图像中没有发光颜色的区域来观察尖晶石、镁铝石、假硅灰石和黄橄榄石。然后可以根据 BSE 和 CL 图像中确定的 f-MgO 区域确定 f-MgO 含量。在实验中，BSE 和 CL 图像在 10 秒内获得。因此，该方法可用于快速测定工业炼钢渣中的 f-MgO 含量。