Pollutants and weathering compounds on medieval bricks of historic buildings from Brasov (Transylvania, Romania)

Abstract

Urban pollution significantly influences historic building preservation via chemical, physical, and biological processes. To plan heritage structure restoration, we must study fired brick mineralogy and its correlation with firing temperature. We must also examine how atmospheric pollutants have affected surface composition over time. This study analyzes medieval bricks from seven medieval buildings in Brașov, Romania. We used physicochemical methods (XRD, SEM-EDS, and FTIR-ATR) to identify brick minerals, estimate firing temperatures, and investigate weathering compounds due to pollutants. Samples show quartz, clay minerals (muscovite, illite, palygorskite/smectite anh., kaolinite anh.), feldspars (microcline, orthoclase, albite, andesine), and carbonates (calcite) (for the bricks estimated to be fired at ∼800 °C); sanidine, gelhenite (for the bricks estimated to be fired at ∼950 °C); anorthite, wollastonite, diopside, spinel, mullite (for the bricks estimated to be fired at ∼1100 °C). Weathering varies by mineralogy, firing temperature, location, and pollutants, including efflorescence (CaCO3), black crust (gypsum, calcite), and organic/bio-organic compounds. Mitigation strategies based on physicochemical studies aim to protect cultural heritage from pollution's adverse effects for future generations. This study is vital globally for preserving cultural heritage, offering insights into mitigating the impact of pollution on historic buildings. It aids in developing universal conservation strategies, ensuring our shared past's longevity and aesthetic value.