Abstract
Among the materials used in constructions, self-healing ones have been widely studied, including polymers, asphalts, cement binders; nonetheless the issue of the implementations and engineering of the self-healing capacity of lime-based mortars has been seldom investigated. As a matter of fact, the aforementioned capacity in restoration of building heritage, as well as in concrete structures, would provide an interesting contribution in terms of durability of the same restoration work as well as of the building as a whole. The aim of this research is to study the influence of healing capacity on the masonry behaviour by means of shear tests. The choice to perform shear tests, with or without lateral precompression is due to the representativeness of conditions truly occurring in masonry structural elements when in service. “Triplet specimens” have been fabricated, consisting of 3 clay bricks and 2 layers of purposed-design mortar, to mimic the compositions of mortars which can be actually found in existing heritage buildings. The methodology envisages three phases: a first series of specimens, after 28 days curing in lab environment, was tested to evaluate the shear strength. Then, on a second series of samples, a damage was induced by loading them to a prescribed fraction (70%) of the shear strength, determined as above in the previous stage; samples were subsequently immersed in water for 3 months and re-tested at the end of this curing period. Results clearly show that the autogenous healing capacity is responsible of an interesting recovery of the interface shear strength. The reliability of this approach has been also investigated by comparing the experimental results with a simplified FE model.
Highlights
In recent years, the use of lime-based mortars in restoration of cultural heritage has increased, because of their chemical-physical and mechanical compatibility with old renders
The water curing of the undamaged triplet specimens has determined an increase of shear strength, which has more than doubled along the investigated three months period
A methodology has been proposed to evaluate the influence of the healing capacity of lime mortars on the mechanical behaviour of masonry subassemblies, by means of brick-mortar interface shear tests
Summary
The use of lime-based mortars in restoration of cultural heritage has increased, because of their chemical-physical and mechanical compatibility with old renders. Instead, cannot be an efflorescence promoter, due to its relevant chemical purity [2]. Due to dissolution, transport and re-precipitation of calcium compounds, it can have autogenous self-healing properties [3,4,5]. The healing capacity might improve the strength of the mortar due to a nice combination of different mechanisms such as dissolution and re-precipitation of calcium compounds and further hydration of un-hydrated binder particles [3]. The healing phenomena may significantly increase the ductility of the mortar, influencing the mechanical behaviour of the whole masonry structure
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