Effect of Dry Deposition of Pollutants on the Degradation of Lime Mortars with Sepiolite

Abstract

[EN] The behaviour of lime mortars containing sepiolite or sepiolite plus pentaclorophenol in atmospheric simulation chambers has been studied. The pollutant gases used in this study have been NO, NO2, and SO2. The studies has been done in wet and dry conditions as well as with and without ozone.

In the case of NO and NO2, the aggressive agent would be HNO3, which reacts with lime mortar binder CaCO3, producing Ca(NO3)2 formation. On this process, the influence of the presence of an oxidant as well as water has been studied. The catalyst effect of the oxidation is known to be accelerated by water presence, so mortars exposed to NO + O3 + H2O and NO2 + O3 + H2O environments undergo a greater salts formation than those exposed to the rest of the aggressive media. The three mortars’ behaviours are similar and independent of their composition, producing small amount of salts in every case.

When SO2 is the gas used, the aggressive agent of mortar will be H2SO4 that reacts with mortar binder, CaCO3 to produce calcium sulphate in the form of gypsum. Oxidant and/or water influence has been studied, and the (SO2 + O3 + H2O) chamber was found to be the one with greater aggressivity to mortars. However, in these conditions, sepiolite presence within the mortars delayed gypsum formation.