Mineralogical, Chemical, and Thermal Characterizations of Historic Lime Plasters of Thirteenth–Sixteenth-century Daulatabad Fort, India

Abstract

Iron ore as pozzolanic filler is an uncommon constituent of historic plaster rarely reported in any research. This paper presents one such study from western India where hematite instead of crushed bricks was identified as admixture in thirteenth–sixteenth-century CE Mughal masonry lime works of Daulatabad Fort. The outer/inner coat plasters from different locations of the fort were examined for morphological, mineralogical, chemical, and basic physical properties. The analytical investigative study was performed by optical microscopy, sieve analysis, X-ray fluorescence, X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, SEM-EDX, and thermal analyzer. Although the plaster is dominantly made of micritic calcite and aggregate, incorporation of gypsum in the outer and inner coats has been detected and probably acted as a second binder. Cannabis sativa was mixed in the plaster, pointing to the knowledge of hempcrete technology by the makers of Daulatabad Fort. This investigation has now provided essential information with enough precision about this historic plaster for formulation of compatible repair materials essential for the site restoration.