The S-RePaIR action explores the use of smart materials based on traditional building techniques as multifunctional intervention agents in historic masonry structures.
Masonry structures of all typologies are commonly encountered worldwide and constitute a large percentage of the architectural heritage inventory, particularly in urban environments. Due to the inherent brittleness of the materials used in traditional masonry architecture, and following the effects of aging, historic masonry suffers from accumulation of damage in the form of cracks and loss of durability. Modern urban development, which includes tunnelling and an increase in ambient vibration due to traffic, is a continuous source of strain on historic masonry buildings.
Preventive maintenance through structural intervention can help protect architectural heritage structures and extend the service life of existing infrastructure. The use of traditional materials is preferred from a conservation engineering standpoint as it maximises aesthetic, chemical and mechanical compatibility between the in-situ and intervention materials. Especially in the case of historic masonry, this translates to the use of lime-based mortars for repointing, rendering or reconstruction. However, lime-based mortars are characterised by low strength and an extended hardening period before for strength development.
Complementing preventive maintenance, structural health monitoring (SHM) is a valuable tool for detecting damage and extraordinary structural deformation in existing structures. Early warning on these effects can help optimise the timing of preventive maintenance, leading to reduced overall intervention costs and reduction of the detrimental effects of damage. However, off-the-shelf sensors for SHM are costly, often suffer from lack of durability and are only able to provide an indirect measurement of damage onset and propagation.
The practical and technological requirements of both preventive maintenance and SHM for protecting historic masonry structures can be satisfied through the use of smart multifunctional materials, namely intervention materials applied for the structural repair and maintenance of structures while also possessing self-sensing capabilities for deformation and damage. Smartness in cementitious materials, such as mortars, can be achieved through enhancement of their piezoresistive properties by means of dispersion of conductive nano- and micro-scale fillers in the material. These fillers include carbon nanotubes, graphite and carbon microfibres, all of which are characterised by different properties and different effects in the materials they are dispersed in.
The primary objective of the project is the development of a smart intervention mortar based on natural hydraulic lime to be used as a repointing agent in historic masonry structures. This is accomplished through the extensive comparison of the mechanical, physical, durability and electromechanical properties of lime-based mortars doped with different types of conductive fillers at different concentrations.
