Distribution depth of stone consolidants applied on-site: Analytical modelling with field and lab cross-validation

An analytical model was applied in order to understand the distribution depth of cured stone consolidants. The model is grounded on a case study of Vienna's St. Stephen's Cathedral and was verified against drilled cores examined by SEM and image analysis, on-site drilling resistance measurements and laboratory-based mechanical tests. The results reveal that the variation of the concentration gradient with penetration depth resembles an exponential decline. The deposition of the cured consolidant is governed by capillary forces upon drying within water-based nano-zirconia dispersions and water/alcohol-based colloidal silica. This effect is less pronounced within reactive consolidants, which undergo polycondensation reactions, as with alkoxysilanes.