Study of ready-mixed plasters applied to the conserva-tion of architectural heritage: comparison between dif-ferent types of binders and aggregates

In recent decades, the use of ready-mixed mortars has become popular in the field of conservation. Recent studies high-lighted that these mixtures do not always ensure durability and compatibility with historical materials. One of the main causes of this issue is the presence of elements that are chemically and physically incompatible with historical materials. Cementitious binders, often found in the formulation of ready-mixed mortars, are a common culprit. Despite the proven compatibility of pure NHL (natural hydraulic lime) plasters with historic materials and their versatility in application due to their hydraulic characteristics, there are still few ready-mixed plasters made solely with NHL avail-able. To gain a deeper understanding of pure NHL plasters, several mixtures were studied using NHL 3.5 and 5 as binders, along with carbonate and siliceous aggregates. Four plasters were formulated, and for each material, tests re-quired by the UNI EN 998-1 (2010) standard were conducted. The results were then compared to understand how the different components influence the macroscopic characteristics of the plasters. The study also considered how the cur-rent standard can provide elements for assessing the benefits of using the products available on the market.