Lime-based nanocomposites for masonry restoration: Towards the implementation of small-scale restoration

The structural integrity of historic and traditional buildings can be affected by natural weathering and incompatible restoration interventions. Traditionally, lime binders have been used extensively for restoration applications, while the incorporation of multi walled carbon nanotubes (MWCNTs) in such a binder, enhances the restoration material with increased mechanical as well as with self-sensing properties due to its piezoresistive characteristics. The focal point of the present investigation was the examination of the electrical, mechanical, and piezoresistive properties of a composite nano-reinforced lime-based mortar paste under different geometrical sizes (scale-up tests). Firstly, prismatic specimens of two different sizes, composed of the proposed nano-reinforced lime-based mortar were subjected to testing and compared against reference prismatic prisms of traditional non-reinforced lime-based mortar with a similar composition. The results showed a 24 % increase in the compressive strength and a 37.5 % decrease in the electrical resistance. Secondly, electrical resistance measurements were carried out on a small-scaled masonry specimen built with the MWCNTs reinforced lime-based mortar, to determine potential structure inhomogeneity effects. The tests revealed approximately 50 % electrical resistance decrease in comparison to the non-reinforced reference prismatic specimens. Lastly, the composite restoration material was applied at an actual masonry restoration project at the public library “Korais” of Chios Island, Greece, with the aim to monitor the composite material’s electrical resistance under real conditions.