Analysis of chemical and physical degradation phenomena of cultural heritage materials and the development of innovative technologies for their protection and conservation

In recent decades, the use of cement has been rampant in the field of plaster restoration of cultural heritage, causing often irreparable damage to our historical heritage and contravening the architectural restoration principles of compatibility, reversibility, and minimum intervention. Cement was immediately considered a better binder than lime due to its greater compressive strength, faster setting, higher adhesion, and waterproofing capacity. It is also cheaper and easier to produce. Portland cement was first produced in the early 19th century, which is why it is absent in the masonry and plastering of many old buildings, as only air lime or hydraulic lime was used. The main current challenge in the field of cultural heritage restoration is to develop new materials or optimise existing ones, reducing energy consumption during production, greenhouse gas emissions and environmental impact. In recent years, there has been a great development of a new type of binders called 'geopolymers', materials with an alumina-silicate base, characterised by a three-dimensional cross-linked structure, through which so-called geopolymer cements can be made. What characterises and distinguishes this innovative cement from Portland cement is a treatment at much lower temperatures (max. 60 - 80°C) and an 80% lower CO2 emission. The suffix 'geo' implies that geopolymers simulate natural rocks in terms of chemical composition and mineralogical structure, of which they exhibit the main properties such as hardness, chemical stability, and durability. The term 'polymer', on the other hand, indicates the type of consolidation process, known as 'geopolymerization', which shares kinetics and mechanisms with polycondensation polymerisation. Recent studies have shown that geopolymeric binders can be obtained from natural raw materials such as pozzolan and synthetic metacaolin, as well as from secondary raw materials such as industrial waste (coal combustion fly ash and blast furnace slag) and excavation waste materials (Neapolitan tuff and cocciopesto). The research project has the twofold aim of analysing the state of conservation of historical buildings, with a specific focus on the lithotypes of Southern Italy, and of developing intervention techniques based on innovative materials that are both compatible with the stone substrates and that favour the transition, also in the cultural heritage sector, towards a sustainable and circular economy.