Penetration depth and redistribution of an aqueous ammonium phosphate solution used for porous limestone consolidation by brushing and immersion

- Redistribution of a consolidant might occur after application in porous materials.
- Redistribution was here investigated for an innovative hydroxyapatite-consolidant.
- Two different application methods (brushing and immersion) were considered.
- Application and drying determine penetration depth and amount of hydroxyapatite.
- Application of a limewater poultice is effective in removing soluble compounds.

When consolidants are applied to porous stones, redistribution may occur inside the pore system after the treatment application, which influences their final penetration depth and performance. In this paper, the kinetics of redistribution were investigated for a 2-step hydroxyapatite-based consolidant, applied by brushing and immersion. The results of the study indicate that both the application method and the drying phase are crucial in determining the final penetration depth, the amount of hydroxyapatite that forms and the redistribution kinetics. In all cases, the limewater poultice applied during the second step of the treatment proved to be effective in removing soluble compounds.