Laboratory of Cultural Relic Conservation Materials, Department of Chemistry, Zhejiang University, Hangzhou 310027, China.
Acc Chem Res. 2010 Jun 15;43(6):936-44. doi: 10.1021/ar9001944.
Replacing or repairing masonry mortar is usually necessary in the restoration of historical constructions, but the selection of a proper mortar is often problematic. An inappropriate choice can lead to failure of the restoration work, and perhaps even further damage. Thus, a thorough understanding of the original mortar technology and the fabrication of appropriate replacement materials are important research goals. Many kinds of materials have been used over the years in masonry mortars, and the technology has gradually evolved from the single-component mortar of ancient times to hybrid versions containing several ingredients. Beginning in 2450 BCE, lime was used as masonry mortar in Europe. In the Roman era, ground volcanic ash, brick powder, and ceramic chip were added to lime mortar, greatly improving performance. Because of its superior properties, the use of this hydraulic (that is, capable of setting underwater) mortar spread, and it was adopted throughout Europe and western Asia. Perhaps because of the absence of natural materials such as volcanic ash, hydraulic mortar technology was not developed in ancient China. However, a special inorganic-organic composite building material, sticky rice-lime mortar, was developed. This technology was extensively used in important buildings, such as tombs, in urban constructions, and even in water conservancy facilities. It may be the first widespread inorganic-organic composite mortar technology in China, or even in the world. In this Account, we discuss the origins, analysis, performance, and utility in historic preservation of sticky rice-lime mortar. Mortar samples from ancient constructions were analyzed by both chemical methods (including the iodine starch test and the acid attack experiment) and instrumental methods (including thermogravimetric differential scanning calorimetry, X-ray diffraction, Fourier transform infrared, and scanning electron microscopy). These analytical results show that the ancient masonry mortar is a special organic-inorganic composite material. The inorganic component is calcium carbonate, and the organic component is amylopectin, which is presumably derived from the sticky rice soup added to the mortar. A systematic study of sticky rice-lime mortar technology was conducted to help determine the proper courses of action in restoring ancient buildings. Lime mortars with varying sticky rice content were prepared and tested. The physical properties, mechanical strength, and compatibility of lime mortar were found to be significantly improved by the introduction of sticky rice, suggesting that sticky rice-lime mortar is a suitable material for repairing mortar in ancient masonry. Moreover, the amylopectin in the lime mortar was found to act as an inhibitor; the growth of the calcium carbonate crystals is controlled by its presence, and a compact structure results, which may explain the enhanced performance of this organic-inorganic composite compared to single-component lime mortar.
修复历史建筑时,通常需要更换或修复砌体灰浆,但选择合适的灰浆往往存在问题。不合适的选择可能导致修复工作失败,甚至可能造成进一步的损坏。因此,深入了解原始灰浆技术并制作适当的替代材料是重要的研究目标。多年来,许多材料都曾用于砌体灰浆中,其技术也逐渐从古代的单组分灰浆发展为包含多种成分的混合版本。公元前 2450 年开始,石灰就已在欧洲被用作砌体灰浆。在罗马时代,石灰中添加了磨碎的火山灰、砖粉和陶瓷屑,极大地提高了性能。由于其卓越的性能,这种水硬性(即在水下能凝固)灰浆得以推广,并在整个欧洲和西亚得到采用。也许是因为缺少火山灰等天然材料,古代中国并没有发展水硬性灰浆技术。但是,中国开发了一种特殊的无机-有机复合建筑材料——糯米石灰浆。这种技术在重要建筑中得到了广泛应用,如古墓、城市建筑,甚至水利设施。它可能是中国乃至世界上第一种广泛应用的无机-有机复合灰浆技术。本文讨论了糯米石灰浆的起源、分析、性能和在历史古迹保护中的应用。对古代建筑中的灰浆样品进行了化学分析(包括碘淀粉测试和酸蚀实验)和仪器分析(包括热重差示扫描量热法、X 射线衍射、傅里叶变换红外光谱和扫描电子显微镜)。这些分析结果表明,古代砌体灰浆是一种特殊的有机-无机复合材料。无机成分是碳酸钙,有机成分是支链淀粉,可能来自于添加到灰浆中的糯米汤。对糯米石灰浆技术进行了系统研究,以帮助确定修复古建筑的适当措施。制备并测试了不同糯米含量的石灰浆。结果表明,引入糯米可显著提高石灰浆的物理性能、力学强度和相容性,表明糯米石灰浆是修复古代砌体灰浆的一种合适材料。此外,发现石灰浆中的支链淀粉起到了抑制剂的作用;其存在控制了碳酸钙晶体的生长,从而形成了致密的结构,这可能解释了这种有机-无机复合材料与单组分石灰浆相比性能增强的原因。