Study of compatibility of biocides and hydrophobizers for the protection of stone monuments in the open air

A long-term monitoring of the protective effect of three soluble in organic solvents and one water-diluted hydrophobizer on limestones with different water absorption was carried out, it was shown that it depends on the degree of water absorption of the treated limestone. Funcosil SNL protected lime-stone with a small water absorption for a longer time than limestone with a large water absorption. On blocks of weathered limestone, MSN-7 was superior to all other tested hydrophobizers. The compatibility of biocides and hydrophobizers used to protect the stone was investigated. The use of biocides from the quaternary ammonium salts (QAC) group either did not affect the protective properties of hydrophobizers, or reduced the duration of protective action. The decrease in the protective effect is determined not only by the recolonization rate of test sites and samples with algae biofilms, but also by measuring the water absorption time and the sorption rate of surface contaminants. In the areas treated with QAC: catamine AB or Capatox and after Funcosil SNL it was higher than in the areas treated only with Funcosil SNL. Surfactant treatment reduced the hydrophobic effect of Funcosil SNL on limestone with low wa-ter absorption to the level of unprotected stone. The degree of impact that the biocidal treatment had before applying the hydrophobizer depended on the solvent in the case of hydrophobizers soluble in organic solvents and on the degree of weathering of limestone. The solvent for Funcosil SNL is white spirit, for MSN-7 - toluene. If, when applying a hydrophobizer, a previously applied biocide with surface-active properties dissolves, this prevents its polymerization process. Some QAC are dissolved in aliphatic hydrocarbons.