Chemical Weathering of Lime Mortars from the Jahangir Tomb, Lahore-Pakistan

Abstract

The effects of environmental pollution on cultural heritage have been widely studied in different parts of the world over the last few decades but not with the reference to Pakistan, although cultural heritage in this part of the world is deteriorating at an alarming rate. Determination of the deterioration processes and causes are the fundamental parameters for the preservation on scientific grounds of these cultural assets. This study investigates the effect of environmental pollution on the facades of the 17th century historic monuments of Jahangir Tomb in Lahore (Pakistan). For this purpose, samples were collected from weathered as well as from sound interior surfaces. The samples were characterized by XRF, XRD, SEM-EDS and stereomicroscopy/wet chemistry to understand the weathering mechanisms and products. Those are mainly comprised of sulphates, chlorides and nitrates along with high contents of soil particulates and biological colonization. Results show that chemical weathering is occurring at the mortar-atmosphere interface of the historic fabric, conjoining the petrographic characteristics of the mortars and enveloping atmospheric composition. This interaction is responsible for the current deterioration of the historic lime mortars.