Development of Restoration Mortars with Enhanced Properties: The Effect of Graphene Oxide-Stabilized Oil-in-Water Pickering Emulsions

Historic buildings are a tangible record of the past and are recognized as part of our cultural heritage, their conservation is aimed at safeguarding its cultural significance for the benefit of present and future generations. The history of construction is based on the use and development of materials with increasing durability to prolong the lifespan of the buildings. Mortar, one of the earliest known building materials, is found in most historic buildings, mainly as a structural binder for bonding masonry units influencing the strength and deformation values of masonry. Mortar lies at the interface between building surfaces and the environment and therefore is most susceptible to degradation as a result of exposure to harsh external agents. Since structural damage of historic buildings mostly consists of mortar depletion and consequent loss of material, there is a need for restoration mortars to fill voids and replace the damaged material. In all efforts toward the conservation of historic buildings, their authenticity should be respected to the greatest extent. Interventions must be in harmony with the original structure, this means that all restoration materials must be aesthetically, functionally, and technically compatible. The durability of ancient Roman mortars and concretes has been evidenced through the continued resilience of the structures in which they were used. The longevity of these ancient building materials makes them an attractive source of inspiration for the design of durable mortar composites. The traditional Roman mortar, as described in Vitruvius’ De Architectura is composed of pozzolanas (natural or artificial), lime, and water. Besides these constituents, the incorporation of additives to improve the mortar properties has been documented, such as the use of linseed oil as a waterproofing agent. Nowadays, different technologies have been proposed to develop mortars with superior performance characteristics; among many additives, the incorporation of GO in lime-based composites is still a novel subject of scientific research. This thesis deals with the development of mortar-based materials suitable for the consolidation of built heritage. In detail, it presents a novel approach to the incorporation of organic additives and two-dimensional nanomaterials within mortars through the design and development of an oil-in-water Pickering emulsion stabilized by graphene oxide (GO). Only a few works are studying the effect of oil and GO in the matrix of natural hydraulic lime mortars experimentally. Studying the effects of the incorporation of such materials and developing improved methods for their incorporation is important for designing a new compatible repair mortar. In this work, mortars with different mixture designs were studied to understand the effect of the addition of linseed oil, GO, and the Pickering emulsion. The addition of linseed oil addition is meant to increase the durability of mortars, but, according to the literature, it results in a decrease in their mechanical properties. The addition of GO could increase the mechanical properties of lime-based mortars used for reparation. The incorporation of GO-stabilized oil-in-water Pickering emulsions could represent a viable strategy for the fabrication of mortar composites that exhibit both enhanced durability and strength.