传统宫殿建筑的红色灰浆常用天然矿物红土作为显色剂, 但由于红土矿被限制开采等原因, 目前古建筑修缮常用工业合成氧化铁红替代红土, 但出现了红灰防水性差、 开裂剥落等现象。 为探究该现象出现的原因, 采集故宫养心殿中三座殿所(正殿、 西围房、 后殿)屋顶的红色夹垄灰样品, 通过X射线衍射(XRD)确定样品的主要物相组成, 结果表明: 各殿样品的主要组成皆为方解石、 氧化铁及石英, 此外含有少量的钠长石及埃洛石。 由于各殿样品色度差异较大, 因此结合粉末微观形貌及Mapping测试, 对比微观颗粒的形态、 颜色及文物样品断面元素分布情况, 结果表明正殿及后殿样品的粉末微观形貌显示为色泽均匀、 饱满的深红色颗粒, 伴有黑色或棕黄色矿物颗粒, 且由元素分布结果可知样品内Fe元素分布不均匀, 且与Al和Si元素分布不一致; 而西围房样品的粉末微观形貌显示为浅色颗粒, 伴有其余矿物组成存在。 元素分布结果表明样品内Fe元素分布均匀, 与Al和Si元素分布一致, 得出正殿、 后殿的红灰样品所用原料及显色物质为白灰、 红土、 氧化铁红; 西围房的红灰样品所用原料及显色物质为白灰、 红土, 首次提出了红土与氧化铁间的鉴别方法。 通过扫描电子显微镜(SEM)探究显色物质对样品微观形貌的影响, 结果表明仅含红土的样品结构连续且致密, 添加氧化铁红后两相结合较差, 孔隙较多。 为进一步探究红土、 氧化铁红对样品性能的影响, 分别制备了添加红土、 氧化铁红的模拟试样, 结合文物样品及分别添加红土、 氧化铁的模拟试样物理力学性能测试结果可知, 用氧化铁红替代红土制作夹垄灰, 相对于用红土制作的夹垄灰, 其物理力学性能较差。

Natural mineral red clay was used as the color agent in red lime of traditional palace buildings. However, due to red clay mining being restricted, iron oxide red synthesized in the industrial method was commonly used to replace red clay in the restoration of ancient buildings, which caused poor water resistance, cracking, peeling, and other that phenomena happened in red lime. In order to explore the cause of this phenomenon, in this study, red Jia-long lime samples were collected from the roofs of three halls (Zheng hall, Xiwei Hall and Hou hall) of Yangxin Hall in the Forbidden city and determined the main phase composition of the samples by X-ray diffraction (XRD). The results show that the main components of the samples are calcite, iron oxide and quartz, in addition to a small amount of albite and halloysite. Since the quite difference in chromaticity of the samples from each hall, it combined powder microscopic morphology and mapping test, comparing the shape and color of the microscopic particles and the element distribution of the sample section to determine the main color components of the red lime sample. The results show that the powder micromorphology of the samples in Zheng Hall and Hou Hall is uniform and full of dark red particles, accompanied by black or brown-yellow mineral particles, and the distribution of Fe in the samples is not uniform and is inconsistent with the distribution of Al and Si elements. However, the powder morphology of the Xiwei Hall sample shows light color particles accompanied by other mineral components. The distribution of Fe elements in the sample is uniform, consistent with the distribution of Al and Si elements. It is concluded that the raw materials and coloring materials used in red lime samples from Zheng Hall and Hou Hall are lime, red clay and iron oxide red. The raw materials and coloring materials used in red lime samples from the Xiwei Hall are lime and red clay. It is the first time that the identification method between red clay and iron oxide red has been proposed. Scanning electron microscopy (SEM) was used to explore the effect of color components on the micro-morphology of the sample, and it was shown that the structure of the sample containing only red clay was continuous and compact, and the two phases were poorly combined after adding iron oxide red, and there were pores. In order to further explore the influence of red clay and iron oxide red on the performance of samples, the simulated samples with red clay and iron oxide red were prepared respectively. It can be seen that the use of iron oxide red instead of red clay to make Jia-long lime has poor physical and mechanical properties compared to the Jia-long lime made with red clay.