Incompatibility stone-mortar Influence of pH on the sensitivity of rocks to saline alterations

This paper discusses incompatibilities between stones and mortars. The aim is to understand the evolution of rocks of acid nature, sandstones in this case, in the presence of mortars of an alkaline nature, such as cement mortars used for jointing or coatings. Accelerated aging tests combining alkaline alteration and salt alteration were simultaneously carried out in order to study the synergy between these two processes of degradation. The degradation process is follow-up by observing the induced alteration patterns, the identification of the newly appeared mineral phases and the evolution of the ultrasonic propagation speed of the materials tested. The obtained results allow showing that the pH-salt crystallization synergy is particularly aggressive towards the studied materials and that the sustainability of the rocks subjected to circulations of basic solutions due to the proximity of mortars of alkaline nature is seriously reduced.