PSI - Issue 78

Riccardo Liberotti et al. / Procedia Structural Integrity 78 (2026) 1919–1926

1924

Table 1. Constituents present in each mix design. Constituent

A B C D E F G H I

L M N

Gypsum

× ×

Lime Sand

× × × × × ×

×

× ×

Black pozzolana Red pozzolana Pozzolanic cement Earthenware powder Alabastrine gypsum Carded sisal fibre

× ×

× ×

×

× × × ×

× ×

×

×

×

× ×

×

Crock powder

× The intervention was brush-applied exclusively on the intradosal surfaces of the latter specimens. The graphs have got the same scale in the x and y axes (force and displacement respectively) to make the comparison between the plots more straightforward. The most notable effect of reinforcement was observed in type A, which showed an increase in peak load of approximately 125% compared to the unreinforced specimens, along with an enhancement in stiffness. Type E also benefited from reinforcement, showing an increase in peak load of approximately 35%, although its stiffness remained essentially unchanged. Further more, for Type E, the presence of two segments with different stiffness values in the force-displacement curve is attributed to the handmade nature of the specimens. In particular, the reinforced sample tested exhibited two non-parallel faces, leading to imperfect contact during the initial loading stage and resulting in a lower apparent initial stiffness. For stiffness comparison purposes, therefore, the second portion of the curve was considered. In contrast, type B showed no significant variation in either stiffness or strength, with the peak load even falling slightly below the average value of the unreinforced specimens. It is important to note that the limited number of specimens in this analysis does not allow for statistical evaluation. Rather, these results should be considered as a preliminary indication of the potential effects of reinforcement on the different specimen types, providing a basis for more targeted investigations. 4. Conclusions This contribution presents the first results of an experimental ongoing research on the mechanical be haviour of various artificially manufactured stone materials that have traditionally been used in ornamental elements of buildings of heritage significance, and which specifically concentrate on mortar-based mixtures. The research has determined, through a controlled comparison between a number of different standard and innovative mix designs, the influence of mineralogical content and additive type on the mechanical behaviour of the mixture. The result of three-point bending tests shows that those mixtures which include pozzolanic materials— such as black pozzolana and pozzolanic cement—display higher peak resistance and overall mechanical strength compared to mixtures relying solely on lime or gypsum binders. Even with added ad vanced additives such as earthenware powder, load carrying capability is also enhanced. Moreover compact alabastrine gypsum-based specimens exhibit a significantly better mechanical behaviour, in terms of duc tility, when carded sisal fibres are introduced in the mixture. Conversely, lime mixes without pozzolanic content showed quite poorer performance, highlighting the importance of mineralogical and chemical com patibility in restoration materials for structural and cosmetic conservation. The campaign test confirms that binder and aggregates choice and right mix ratios are of most importance in determining the mechanical properties of restoration mortars in line with requirements. These findings provide a useful reference point for formulating consolidants and protective coatings with adherence to the core principles of architectural conservation—transparency, reversibility, and compatibility. In particular, a strengthening procedure, with a coating based on TEOS and graphene, is proposed in this paper obtaining very interesting enhancement of the mechanical behaviour. In the future perspective, additional tests will involve also more prototypes consolidated, since so far the experimental campaign led to promising results, both in terms of strength ening and compatibility related to historical architectural elements. Different experimental characterization programs will be also performed to qualify the chemical-physical features of the proposed intervention.