Integrated Architectural Documentation and Multi-Analytical Characterisation of Historic Lime Mortars in the Tomb of Ali Mardan Khan, Lahore, Pakistan

Abstract

Mughal architectural heritage conservation needs a holistic understanding of its spatial organisation and the performance of its construction systems. This research investigates the Tomb of Ali Mardan Khan in Lahore, a 17th-century (1656-1657) Mughal funerary building, in terms of architectural recording and material analysis. The monument is a mature example of Mughal architecture with an octagonal plan, a double-dome structure, a high drum, chattris and a sophisticated decoration. Despite its historical and architectural importance, the structure is in a state of severe deterioration, as a result of environmental factors, plant growth and unsympathetic restorations. We employed a multi-disciplinary approach, which combined architectural documentation with laboratory analysis for material characterisation, specifically X-ray fluorescence (XRF), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy with energy dispersive X-ray analysis (SEM-EDX) and water absorption. The architectural survey captured the spatial arrangement, structural hierarchy, and the decorative elements of the tomb, including the entrance, dome system, burial chamber and other decorative elements. XRF analysis shows high lime content (calcium and silica), consistent with non-hydraulic lime mortars with siliceous aggregates. FTIR analysis confirms calcite as the dominant binding phase, and SEM-EDX shows a highly porous structure with a weak bond between binder and aggregate, and small hydraulic phases. High porosity and water absorption are also confirmed by water absorption tests. This combined approach shows a high level of incompatibility between original lime-based materials and subsequent cementitious repairs, accelerating the deterioration of materials. The research emphasises the need for compatibility-based conservation and the use of architectural documentation and material science for evidence-based restoration of Mughal monuments.