New Nanomaterials for Consolidation of Calcareous Stones and Stone-Like Artifacts

To cope the problem of deterioration of calcareous historical building materials, increasingly threatened by natural hazards and anthropogenic activities, two new calcium alkoxides were developed during the European NANOMATCH project (funded under FP7 GA no. 283182) as effective consolidation materials at nanoscale level. Two products (Calcium tetrahydrofurfuryloxide and Calcium ethoxide) were firstly designed, then synthesized in lab and finally produced on a Kg/Lab scale in industrial pilot plant. The consolidation efficacy was eventually tested through their nanosuspensions' application on stone and stone-like model samples and on historical surfaces and the performance compared with the one of commercial consolidants. Some samples were exposed in 4 sites located in different countries to evaluate their durability towards different weathering agents [1]. Preliminary risk assessment on release of nanoparticles was performed too. The NANOMATCH products based on calcium alkoxide demonstrated to be a possible solution for the consolidation of lime-based stone and stone-like materials, thanks to their ability to penetrate the substrate, to turn on corresponding carbonates and, forming nanosized particles and/or coating, to well adhere to the original mineral structure, restoring integrity and mechanical properties. According to the tests performed, the treatments resulted compatible and efficient, with no safety concerns for human health and environment related to their nanostructure. Despite the good consolidation properties, they evidenced some problems of instability and purity; our research efforts are currently focusing on these problems that need to be solved before introducing the products in the restoration market.