气候对中国古代塔砖材料性能劣化影响的研究

在气候影响下,塔砖材料性能的劣化加剧了中国古塔结构的损伤,减少了古塔的结构寿命。为此,课题选择两个极具代表性的中国古代砖塔—1500年历史的嵩岳寺塔和1200年历史的法王寺塔进行同一性研究,欲证明两塔在地理位置、环境气候、形制、塔体古砖制造原料和制造工艺等方面均具有很强的相似性和同一性。采用X射线荧光光谱法分析了两塔塔砖的材料成分,采用压汞法对两塔塔砖材料的孔隙率、孔隙结构和孔隙分布特征进行了实验。两塔塔砖材料实验结果的差异证明:在公元5世纪到公元8世纪的300年气候影响下(该气候为自然营力而非实验室人工模拟),塔砖材料孔隙率的增大是导致中国古代塔砖性能劣化的主要原因,大约30%左右的孔隙从小于1000nm孔径发展扩大到10000～50000nm孔径是塔砖材料孔隙率增大的主要表现形式。因此,预防小孔径孔隙(小于1000nm)在气候影响下发展扩大的防治措施应该成为中国古代砖塔保护工作的研究重点。同时,对因塔砖材料性能劣化而产生的古塔塔体的表观特征进行了分析,分析结果有利于中国古代砖塔的保护。

The effect of climate on the deterioration of ancient tower bricks

Tower bricks deterioration due to climate influence accelerate ancient towers' damage and decrease their life expectancy. Two representative ancient Chinese brick towers-Songyue Temple brick tower (about 1500 years old), and Fawang Temple brick tower (about 1200 years old) were selected as the subjects for a comparative study. In this study, it was found that they have common characteristics and similarities in geographic location, surrounding environment and climate, appearance and structure, the raw materials and brick manufacturing techniques etc. X-ray fluorescence spectrometry was employed to analyze the material composition of the towers' bricks; the mercury intrusion method was employed to test the brick porosity, brick pore size and pore distribution characteristics. The experimental results showed that an increment in porosity from 5th century to 8th century was the main index of ancient Chinese brick towers deterioration. About 30% of the porosity with small pore size in the 1000 nm diameter expanded to 0,0~0,0 nm. Therefore, to prevent small pore size (less than 1000 nm diameter) from expanding under the influence of the climate is the key of research to protect ancient Chinese pagoda towers. The appearance characters of ancient towers because of deterioration of brick materials are also described to preserve ancient Chinese towers made of bricks.