Conservation of weathered historic sandstone with biomimetic apatite

Abstract

The conservation of weathered historic sandstone with apatite was studied. Based on the growth mechanism of bone, calcium and phosphorus were introduced into weathered sandstone and then mineralized at room temperature. The conservation efficiency was investigated by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), selected area electron diffraction (SAED), X-ray diffraction (XRD), and compressive strength, capillary water uptake, water vapor permeability and weather resistance tests. The SEM, EDX, TEM, SAED and XRD results showed that the produced hydroxyapatite could reunite the weathered stone blocks and provide sufficient reinforcement to hold them together. The results of the various tests indicated that the compressive strength and weather resistance of the treated samples was improved significantly. In addition, because of the porous nature of apatite, the water vapor permeability of the treated stone was not affected and its breathability was maintained.

The CRATI Project: New Insights on the Consolidation of Salt Weathered Stone and the Case Study of San Domenico Church in Cosenza (South Calabria, Italy)

“…This increase in the properties of cohesion and mechanical strength are due to the formation of hydroxyapatite [21]. Several studies report the strengthening effectiveness of this treatment, especially on porous lithotypes [43][44][45].…”

Comparative Study Between Ammonium Phosphate and Ethyl Silicate Towards Conservation of Prehistoric Paintings in the Magura Cave (Bulgaria)

“…Thanks to the low viscosity of the phosphate solution and to the absence of nanoparticles, a good penetration depth is usually achieved (>5 cm in highly porous limestone) [25]. So far, the treatment has provided good results on a variety of substrates [25], including many types of natural stones [26][27][28][29][30][31][32], mortars [33,34], and stuccoes [35]. Recently, the interaction between ammonium phosphate solutions and pigments used in wall paintings has been investigated, and, in most of the cases (but not in all), the treatment has been found to cause negligible color changes [36].…”

New nanomaterials for applications in conservation and restoration of stony materials: A review

“…However, differently from samples consolidated with TEOS, hydroxyapatitetreated stones experienced very low variations in porosity and pore size distribution, leading to substantially no variation in the rate of water sorption and a small decrease in water vapor permeability (68). On the other hand, the HAP has been tested as a protective treatment for marble against acid rain corrosion, showing an improvement in the marble resistance to the dissolution (69,71).…”

“…They determined the application of HAP by brushing as the most suitable method. This methodological application induced a significant mechanical improvement of limestones with limited microstructural, physical and chromatic alterations (69). Furthermore, Sassoni et al (73) studied the effectiveness and compatibility of hydroxiapatite treatment for limestone, in comparison with ethyl silicate.…”