Study for the production of a new sustainable additive for restauration mortars

The strong demand for innovative and sustainable materials for the conservation and the restoration of cultural goods represent a fundamental point in current research in the cultural heritage field. In this context, the NYMPHA project propose a new solution for the restoration and conservation of works of art made of different materials, through the use of a mixture of polysaccharides extracted from microalgae cells (Masi et al., 2021). To this aim, a sustainable protocol for the extraction and purification of polysaccharides has been designed using the unicellular microalga Chlamydomonas reinhardtii. The final product has been characterized from a chemical (FT-IR, Raman and quantitative essays) and biological point of view (antioxidant tests and analysis of resistance to biological attack). From the laboratory characterization, it was possible to compare the polysaccharides composition and the total sugar concentration present in the polysaccharide mixture extracted from Chlamydomonas reinhardtii with other commercial polysaccharides widely used in the restoration sector. Experiments based on polysaccharide extracts applications on several materials were performed to evaluate their efficacy as consolidant. First of all, tests were carried out on organic (wood and paper) and inorganic surfaces (white marble). Then, the polysaccharide extract was added in restoration mortar. The aim was to contribute to the needs of heritage buildings conservation activities by providing an economical, sustainable, and non-toxic additive with a great level of compatibility with ancient materials. Several samples were realized to evaluate the efficacy of NYMPHA product as additive: samples with two different extract concentration, samples with Primal B60 (acrylic resin) as typical restoration additive and sample without additives as reference. Physical properties of the samples were tested before and after the artificial ageing period in climate chamber and UV chamber, to evaluate differences in mechanical resistance, surface wettability, capillary ability, variation in porosity and to estimate the preservation of the aesthetic characteristics, with colorimetry test. Moreover minero-petrographic and chemical analyses, such as optical microscopy, XRPD, SEM-EDS and FT-IR were realized in order to evaluate changes in the mortar texture, as well as the enhancement of the carbonatation process and, consequently, the consolidation property of the product here proposed. Masi A., Medeghini L., Masi A., Sadori L., Leonelli F., Favero G. & Antonacci A. (2021) - Natural polysaccharides from microalgae for the protection of cultural heritage. SMART eLAB, 16, 24. https://doi.org/10.30441/smartelab.v16i.127