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<p>This study provides a multi-analytical characterisation of historic lime plaster samples from the Se Cathedral, Old Goa, to assess their microstructural integrity, mineralogical composition, and carbonation behaviour within a humid tropical–coastal regime. Six samples (L1–L6) representing interior decorated masonry and exterior collapsed-tower contexts were analysed using SEM–EDX, XRD supported by crystallinity index (CI) analysis, FTIR–ATR spectroscopy, and SEM-based particle-size distribution modelling using Gaussian fitting. SEM observations revealed a predominantly fine-grained calcite binder matrix, with interior plasters exhibiting very fine binder fractions (0.6–1.0&#xa0;μm; mean ~ 0.99&#xa0;μm) embedded with quartz and orthoclase inclusions derived from local geological sources. These microstructural features suggest enhanced mechanical cohesion, pore regulation, and vapor permeability. Consistently, interior samples displayed lower crystallinity (≈ 38–45%), indicating restricted carbonation due to high humidity, limited air circulation, and salt-laden microenvironments. In contrast, exterior plasters exhibited markedly coarser particle fractions (≥ 14&#xa0;μm) and higher crystallinity (up to ≈ 50%), reflecting prolonged exposure to atmospheric CO₂ and open-air weathering. FTIR spectra confirmed calcite as the dominant phase, with minor siliceous and clay-derived inclusions, while EDX data showed Ca-rich matrices indicative of controlled lime–sand mixing practices. Although direct pozzolanic reactivity tests were not undertaken, mineralogical, spectroscopic, and microstructural signatures collectively suggest the presence of siliceous or weakly hydraulic components—an analytical limitation with recommendations for Chapelle, Frattini, and TG-based follow-up investigations. These spatially resolved findings highlight the adaptive technological choices embedded in traditional lime formulations and provide critical insights for designing compatible conservation mortars for coastal heritage environments.</p>

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Investigating the durability and carbonation patterns of historic lime plasters using SEM, XRD, FTIR and crystallinity indices

  • 期刊论文

  • 发表日期：

    2026年3月13日

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  • Manager Rajdeo Singh,
  • Madhuri Sawant,
  • Asadulla Asraf Ali

摘要

This study provides a multi-analytical characterisation of historic lime plaster samples from the Se Cathedral, Old Goa, to assess their microstructural integrity, mineralogical composition, and carbonation behaviour within a humid tropical–coastal regime. Six samples (L1–L6) representing interior decorated masonry and exterior collapsed-tower contexts were analysed using SEM–EDX, XRD supported by crystallinity index (CI) analysis, FTIR–ATR spectroscopy, and SEM-based particle-size distribution modelling using Gaussian fitting. SEM observations revealed a predominantly fine-grained calcite binder matrix, with interior plasters exhibiting very fine binder fractions (0.6–1.0 μm; mean ~ 0.99 μm) embedded with quartz and orthoclase inclusions derived from local geological sources. These microstructural features suggest enhanced mechanical cohesion, pore regulation, and vapor permeability. Consistently, interior samples displayed lower crystallinity (≈ 38–45%), indicating restricted carbonation due to high humidity, limited air circulation, and salt-laden microenvironments. In contrast, exterior plasters exhibited markedly coarser particle fractions (≥ 14 μm) and higher crystallinity (up to ≈ 50%), reflecting prolonged exposure to atmospheric CO₂ and open-air weathering. FTIR spectra confirmed calcite as the dominant phase, with minor siliceous and clay-derived inclusions, while EDX data showed Ca-rich matrices indicative of controlled lime–sand mixing practices. Although direct pozzolanic reactivity tests were not undertaken, mineralogical, spectroscopic, and microstructural signatures collectively suggest the presence of siliceous or weakly hydraulic components—an analytical limitation with recommendations for Chapelle, Frattini, and TG-based follow-up investigations. These spatially resolved findings highlight the adaptive technological choices embedded in traditional lime formulations and provide critical insights for designing compatible conservation mortars for coastal heritage environments.