Characterization of ready-mixed plasters for the conservation of architectural heritage

Nowadays, the use of ready-mixed mortars is widespread in the choice of materials for the conservation of architectural heritage. These are dry mixtures, which contain binders, aggregates and additives and which require only the addition and mixing with water. Their use makes it possible to avoid errors in the ratios of the components, limits waste and guarantee a constant product quality. On the other hand, there are no standards that require the declaration of all the components in the mixture, which makes difficult to select the most appropriate materials to use on historical substrates. Indeed, the presence of certain additives could alter other properties of the mortars or increase the probability of developing forms of degradation. In addition, the mixtures on the market are frequently labelled as environmentally, human and animal health friendly; but the actual sustainability of these mixtures is difficult to ascertain, because there are still few companies that study the Life Cycle Assessment (LCA) and publish the Environmental Product Declaration (EPD) of their products. In order to deepen the knowledge of this class of materials, this study proposes the characterization of five ready-mixed plasters, all labelled green by the companies. Analyses (X-ray diffraction, infrared spectroscopy, thermal analysis) have been carried out firstly to assess the compatibility of the mixtures with historical materials, to compare the results obtained with what is stated by the companies in the product data sheets, and to assess whether, through routine laboratory analyses, it is possible to certify the sustainability of these materials.