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

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.