Spectral Properties of Sulfated Limestone and Marble: Implications for In Situ Assessment of Atmospheric Pollution Damage to Carbonate Rock Building Materials

Abstract

Infrared spectral reflectance of Salem Limestone and Shelborne Marble exposed to simplified artificial weathering by dilute sulfuric acid solutions is studied as a function of the concentration of surficial gypsum formed. Data presented indicate that calibration curves relating gypsum concentration to reflectance band strengths at 1.93, 6.5, and 8.5 μm can be constructed for both limestone and marble and that nondestructive quantitative compositional analysis is possible using either near-infrared (NIR) or mid-infrared (MIR) measurements. The preferred spectral region depends on the nature of the carbonate material under attack and the amount of gypsum formed. Detection limits for gypsum established for both the limestone and the marble indicate these spectroscopic techniques could provide a viable tool for early monitoring of the effects of certain atmospheric pollutants on carbonate rock building materials.