Characterization and compositional identification of Stepwell (Baoli) lime plasters from 16 th Century Arab

Abstract

Abstract The present work deliberates on a 16th-century stepwell lime plaster sourced from Arab Ki Sarai, Humayun tomb complex, Delhi. The plaster samples were observed under an analytical microscope, and the thin section was examined through petrological analysis. The samples were also investigated using analytical techniques of XRF, FTIR, XRD, SEM-EDX, and thermal analysis. The brick-lime junction of the plaster studied using FTIR, XRD, and EDX analysis indicated that the brick aggregates have played a major role in improving the mechanical strength and permeability for better carbonation of the lime and hardly influenced hydraulicity. The comparative study of brick, brick-lime interface, and lime layer showed clear mineralogical and compositional changes. The bricks used as aggregates were fired at high fusion temperatures, destroying the crystalline structure of clay minerals and causing loss of pozzolanic activity due to reduced surface area and formation of high-temperature mineral phases. Studies indicate brick-lime inclusion in the plaster layers, and coarse brick aggregates fired at elevated temperature was specifically selected for underwater construction. The FTIR and thermal analysis indicate mixing a minor quantity of proteinaceous adhesive during plaster preparation, but organic additives like jute fibers were not added.