LAUSR

Abstract Mortar is the most common component of the construction materials used for centuries. The use of admixtures is essential in preparing mortar mix with mechanical properties suitable for the restoration of ancient structures. In the present study, Natural Hydraulic Lime (NHL3.5) mortar was modified by adding Egg Albumen (EA) as an admixture in varying concentrations of 0.1%, 0.2%, and 0.3% by weight of water, and tested for their fresh-state, mechanical, physical, and durability properties. The rationale behind the work is that the protein-rich Egg Albumen could increase workability due to their lubricating and viscous nature, besides enhancing mechanical properties due to their adhesive nature that could effectively bond the lime and sand together. The work's main objective was to investigate the fresh and hardened state properties of EA-modified hydraulic lime mortar and to discuss the results. The scope of the present study includes (i) evaluation of the effect of EA on the mechanical properties of NHL3.5mortars, (ii) an assessment of the influence of EA on the microstructure and porosity of the NHL3.5mortars, and (iii) durability assessment of the modified mortars based on the reduced capillary water uptake. Analytical techniques such as Fourier Transform Infrared Spectroscopy, X-ray Diffraction, and Thermogravimetric Analysis were used to study the modified mortar's microstructure. Proteins form an impermeable hydrophobic layer that restricted the penetration of water. As a result, the connectivity between the EA-modified-NHL 3.5 mortar's pores was disrupted, resulting in the decreased capillary intake of water and salt solutions. Therefore, EA-modified NHL 3.5 mortars, with their upgraded workability, mechanical, and durability properties, are considered a new generation of sustainable admixtures that could preserve heritage value structures and assure potential use in modern construction.