Consolidation of Stone Materials by Organic and Hybrid Polymers: An Overview

Historic stone buildings and monuments undergo a gradual, unstoppable, and episodic deterioration due to environmental or climatic impact, biological or mechanical deterioration, or, in the case of better-preserved structures, inadequate maintenance. Water infiltration, freezing and thawing, carbonation, wind erosion, acid rain, and graffiti/vandalism are the key “environmental” issues that strongly impact cultural heritage and therefore must be limited or even prevented. This interaction leads to the occurrence of different phenomena, possibly involving blistering phenomena on the stone surface, its gradual weather away, leaving a sound surface behind, or the dropping away of the bulk material, because of prolonged weathering, in a single event. It is noteworthy that, quite often, the stone may appear perfectly intact to the naked eye, though it is losing its cohesion beneath its surface. Therefore, it becomes necessary to either efficiently protect the stone substrates to prolong their life, or to fix the damage that already occurred by means of effective, reliable, and long-lasting consolidation/restoration strategies. This work aims at summarizing the current state-of-the-art referring to the use of monomeric/oligomeric or polymeric consolidants, providing the reader with some perspectives for the next future.