Evaluating the carbonation degree of concrete using the carbonation zone width provides more accurate results than using the carbonation depth determined via pH indicators. In this study, a testing and calculation method for the carbonation zone widths of recycled aggregate concrete (RAC) was developed. The method was applied after the old mixed mortar (OMM) and new mixed mortar (NMM) were distinguished using iron oxide. The effects of the type and replacement ratio of the recycled coarse aggregate, carbonation period, and sampling location on the carbonation zone widths of the RAC were investigated. Furthermore, the mathematical relationships between the carbonation depths and carbonation zone widths were analysed. The results indicated that the carbonation zone widths were significantly larger than the carbonation depths. Additionally, using samples of OMM and NMM yielded significantly different results. Therefore, selecting a larger carbonation zone width can avoid overestimation of the carbonation service life of concrete structures. Furthermore, polynomial and logarithmic functions were suggested for the calculations of the carbonation zone widths when selecting NMM and OMM samples, respectively. This study is useful for engineers because the findings can assist in evaluating the carbonation degree of concrete and the carbonation service life of structures according to the carbonation depth.

与使用通过pH指示器确定的碳化深度相比，使用碳化区域宽度评估混凝土的碳化程度可提供更准确的结果。在这项研究中，开发了一种测试和计算方法的再生骨料混凝土（RAC）的碳化区宽度。在使用氧化铁区分旧混合砂浆（OMM）和新混合砂浆（NMM）之后应用该方法。研究了再生粗骨料的类型和置换率，碳化时间和采样位置对RAC碳化区宽度的影响。此外，分析了碳化深度与碳化区宽度之间的数学关系。结果表明，碳化区宽度明显大于碳化深度。另外，使用OMM和NMM样本得出的结果明显不同。因此，选择较大的碳化区宽度可以避免高估混凝土结构的碳化寿命。此外，当分别选择NMM和OMM样品时，建议使用多项式和对数函数来计算碳化区的宽度。这项研究对工程师有用，因为这些发现有助于根据碳化深度评估混凝土的碳化程度和结构的碳化使用寿命。当分别选择NMM和OMM样品时，建议使用多项式和对数函数来计算碳化区的宽度。这项研究对工程师有用，因为这些发现有助于根据碳化深度评估混凝土的碳化程度和结构的碳化使用寿命。当分别选择NMM和OMM样品时，建议使用多项式和对数函数来计算碳化区的宽度。这项研究对工程师有用，因为这些发现有助于根据碳化深度评估混凝土的碳化程度和结构的碳化使用寿命。