Gabriela Graziani

Consolidation of porous carbonate stones by an innovative phosphate treatment: mechanical strengthening and physical-microstructural compatibility in comparison with TEOS-based treatments

For preservation of stones used in Cultural Heritage, affected by weathering processes that threaten their cohesion and mechanical properties, the application of consolidants is a common practice. However, available consolidating products generally exhibit some drawbacks that hinder their performance, in terms of either mechanical efficacy, compatibility with the substrate and/or durability. Ethyl silicate is currently the most widely used among stone consolidants; nevertheless, its reduced efficacy on calcitic substrates, together with its temporary hydrophobicity, its tendency to crack and its common formulation with volatile organic solvent, make the research for alternative consolidants for carbonate stones necessary. In this paper, a recently proposed new consolidation treatment based on the formation of hydroxyapatite inside the stone was tested on two different porous carbonate stones (Globigerina Limestone and Giallo Terra di Siena), and compared with TEOS-based treatments, frequently used for the consolidation of these lithotypes. The results show that the hydroxyapatite treatment exhibits a good efficacy in terms of mechanical properties and, compared to TEOS, it causes less pronounced alterations in open porosity and water transport properties. This makes the new treatment a potentially valid alternative to TEOS, especially in those situations where the possible presence of water behind the consolidated layer (e.g. in case of rising damp, condensation or infiltration) might threaten the durability of the consolidation intervention.

Mechanical properties of fired-clay brick masonry models in moist and dry conditions

Rising damp is one of the main issues affecting masonry buildings. However, its consequences on the mechanical performance of masonry structures are not so largely explored. In this paper, the compressive and shear behaviour of masonry triplets, manufactured with solid fired-clay bricks and cement-based mortar, is investigated in dry and moist conditions. The results are interpreted on the basis of the features of the single materials, from both a mechanical and microstructural point of view.

A Nanomechanical Investigation of Engineered Bone Tissue Comparing Elastoplastic and Viscoelastoplastic Modeling

It is common practice to implement the elastoplastic Oliver and Pharr (OP) model to investigate the spatial and temporal variations of mechanical properties of engineered bone. However, the viscoelastoplastic (VEP) model may be preferred being envisaged to provide additional insights into the regeneration process, as it allows evaluating also the viscous content of bone tissue. In this work, the elastic modulus (), contact hardness (), hardness (), and viscosity index () of newly formed bone tissue regenerated at 4 and 12 weeks from the implantation of a macroporous hydroxyapatite scaffold in a rabbit femoral critical-size model were addressed and compared to the mechanical properties of preexisting bone. Indentation curves were fitted with both the OP and VEP models. The VEP model outlined a wider gap between the mechanical properties of native and regenerated tissue when compared to the OP model. In addition, the VEP model indicated an increase of the viscosity index from 4 to 12 weeks, supporting the evidence of a still active regeneration process. The reported results confirmed the higher ability of VEP model compared to the more diffused OP model to provide important insights into bone mechanical properties, also during the bone regeneration process.