Influence of age of fermented Terminalia chebula fruit extract in shell lime: An ancient lime putty production technique adopted in Indian heritage structures

Abstract

The study examines the influence of fermentation age of 5% w/v extract (K5%) of Terminalia chebula fruit in shell lime, using a 0.75 K5%-to-binder ratio. The carbon dioxide evolution, UV-Spectrometric analysis of K5% followed by Gas chromatography and mass spectroscopy (GC-MS) of the slaked putty variants, identified the predominance of organic acids, fatty acids, and esters. The 90th day physical, mechanical, and durability testing confirmed the lowest water-accessible porosity at 31.07 ±0.11% v/v in K5%-4-90, with capillary porosity trending as K5%-4-90<K5%-7-90<K5%-14-90<R-90<K5%-1-90, affecting compressive strength. Mineralogical and morphological studies confirmed the formation of calcite (CaCO3) polymorphs and calcium oxalates via the oxalate-carbonate pathway. Further, thermogravimetric analysis (TGA) revealed the highest %CaCO3 in K5-4-90 and K5-7-90 samples, linked to carbonation extent. The study specifies that K5% at the 4th and 7th days of fermentation age significantly alters putty characteristics, supporting its widespread application and internal and external finishes in heritage structures.