Atmospheric deterioration of cement plaster in a building exposed to a urban environment

The work presents results achieved in a research study on the effects of atmospheric deposition on the cement mortar of the basement in a twentieth-century building located in the city of Ancona (Italy). The degree of damage as a function of the sampling depth is evaluated by combining visual observation, scanning electron microscopy, X-ray diffraction, ion chromatography, differential and gravimetric thermal analysis and the quantitative determination of elemental carbon. Sulphation is found to be the main damage mechanism occurring on the cement mortar constituting the base section of a building since the concentration of sulphate increases from the inner to the outer layer at the expense of the carbonate. The absence of sulphite indicates a direct formation of sulphate, possibly due to the catalytic effect of heavy metals present in the carbonaceous particles of the black crust. Insoluble sulphates, such as ettringite, do not form at the surface, but within a deeper layer of the basement due to its instability to atmospheric carbon dioxide.