A scientific study on the role of organic lime mortars of Padmanabhapuram Palace, Thuckalay, Tamilnadu, India

TLDR: In this paper, the authors provided the scientific evidence of ancient construction practice and production technology on the use locally available geo-earth materials and natural herbs, namely kadukkai (Terminalia Chebula), neelamari (Indigofera tinctoria), hibiscus (Rosa sinensis), palm jaggery (Borassus flabellifer), aloe vera (Aloe barbadenis) as specified in ancient palm leaf texts which were adopted at Padmanabhapuram Palace, India for preparing the traditional lime

Abstract: This research aims at providing the scientific evidence of ancient construction practice and production technology on the use locally available geoearth materials and natural herbs, namely kadukkai (Terminalia Chebula), neelamari (Indigofera tinctoria), hibiscus (Rosa sinensis), palm jaggery (Borassus flabellifer), aloe vera (Aloe barbadenis) as specified in ancient palm leaf texts which were adopted at Padmanabhapuram Palace, India for preparing the traditional lime mortars. Six mortar samples of three different mortar typologies (wall, bedding and floor finish) were taken from the Padmanabhapuram Palace for the study. The sampled mortars were characterized using physiochemical analysis as well as modern analytical techniques including XRD, TG-DTA, FT-IR and FESEM-EDX methods. Different binder-to-aggregate ratios was proportioned for wall plaster (1:3), bedding mortar (1:2) and floor finish (1:1) and was confirmed through acid loss analysis. Wall plaster samples indicated the presence of organic protein and polysaccharide spectral peaks substantiated by FT-IR analysis. Organics have played a significant role in the formation of calcium aluminate silicates and carbonate polymorphs to enhance the crystalline hydrated phases observed through XRD and FESEM analyses. The thermal investigation substantiated that calcite decarbonation mostly occurred between 705 and 730 °C. The results apprised the wide use of hydraulic lime with fine-grained aggregate particles, added with fermented organics to produce an environmentally friendly organic mortar to restore the structure.