Stone consolidation by treatment based on diammonium hydrogenphosphate and calcium hydroxide nanoparticles

Recently the interest in application of nanomaterials for preservation of Cultural Heritage increased. The study proposes a method for the consolidation of weathered calcareous stone (i.e. Lecce Stone) by diammonium hydrogenphosphate and calcium hydroxide nanoparticles providing hydroxyapatite. Stone specimens were artificially weathered by wetting-drying and freezing-thawing cycles and then treated with the products. The mineralization process affording hydroxyapatite was carried out at room temperature, by mimicking the growth mechanism of bone. Ca(OH)2 nanoparticles were synthesized and characterized by X-ray diffractometry (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and dynamic light scattering (DLS). The progression of apatite in stone substrate was studied by XRD, its distribution by SEM-EDS. The Treatment efficacy was evaluated by tests as water capillary absorption, colorimetric measurements, tape test, resistance to salt crystallization and uniaxial compression. The results about biomimic formation of hydroxyapatite represent a promising method for conservation of calcareous materials as Lecce Stone