Investigation of microstructure characterization of mortars from 800 years old heritage structures in Southern part of India

The paper describes the details of the masonry mortars of 800 years old heritage sites, namely Ramappa Temple, a candidate UNESCO World Heritage (2019-2020) site, and secondly, an ancient fort both in Southern part of India. These heritage structures require maintenance repairs particularly at masonry joints for posterity. Characterization of these ancient mortars is essential to understand the quality and also for developing compatible repair mortars. The physical analysis including porosity, bulk density and specific gravity of ancient mortars were computed and it was found that the mortar samples were highly porous. Analytical techniques like XRD, SEM-EDS, XRF, TG-DTA and FTIR were conducted to study the mineralogical and chemical composition of the ancient mortars. From TG-DTA, it can be observed that the binders varied from weak to moderately hydraulic. This was further confirmed from the hydraulic index of binders in mortar samples of these heritage structures. The FTIR analysis inferred possible presence of carbohydrates. The mineralogical analysis signifies the presence of calcite and quartz minerals along with traces of vaterite and aragonite-which are the polymorphs of calcium carbonate (CaCO3) along with feldspar. The lime was of calcitic origin with siliceous aggregates.