Exposure tests of building materials in urban atmosphere

Samples of stones and mortars (air setting and hydraulic) characteristic of ancient masonry and modern conservation works were exposed in Milan and Ancona for a period of 6, 12 and 24 months. After exposure, the samples were analysed. As previously observed on carbonate rocks, the data obtained highlight that sulphation also occurs on mortars (which are more reactive than stones), producing an intermediate product, i.e. calcium sulphite. Sulphate and sulphite, alongside nitrate and nitrite, typical of urban atmospheric deposition, were found in greater amounts in the samples exposed in Milan, while chloride, a typical sea-site tracer, was found higher in Ancona.