A new proposed semi-quantitative method for the organic additives analysis in traditional lime mortar

• Published in: Journal of cultural heritage 2023-07, Vol.62, p.284-292
• Main Authors: Zhai, Kuanrong, Zhang, Bingjian, Zhu, Longguan
• Format: Article
• Language: English
• Subjects: Historical buildings preservation; Lime mortar; Organic additives; Quantitative analysis methods
• ISSN: 1296-2074; 1778-3674
• DOI: 10.1016/j.culher.2023.06.003

•A series of semi-quantitative analytical procedures are proposed for the characterization of organic additives in ancient lime mortars and can be a preliminary screening method for further lab analysis.•The use of a microplate spectrophotometer reduced the detection limit by two orders of magnitude and decreased the sample consumption to 0.2 g for the detection of seven organic substances.•Twelve samples of ancient mortar from the Forbidden City in Beijing were analysed using the test procedure. To improve the performance of lime mortar, ancient craftsmen often added various additives to mortars, including inorganic and organic materials. The analysis of mortar additives plays an important role in the conservation and restoration of historical buildings. However, it is quite difficult to accurately identify the species of additives. This paper proposed a series of semi-quantitative analytical procedures to identify the organic additives in ancient lime mortars. By using reagents such as phenolphthalein, periodic acid, acetylacetone, anthrone, bicinchoninic acid (BCA), iodine-potassium iodide, chloramine T, etc., organic additives such as triglyceride, soluble sugar, starch, and protein (including blood, gelatine, and other unknown proteins) remaining in ancient lime mortar were accurately detected, respectively. The linear relationship of the standard curve was significant, and the detection limits for the target additives were below 7 µg/mL. The process is easy to operate within 6 h, and it is suitable for rapid in-situ testing.