Microstructural modifications of lime-based mortars induced by ceramics and nanoparticle additives

Abstract

Lime-based mortars are one of the principal choices for building and restoration projects, owing to their unique qualities and material compatibility. Admixtures have long been incorporated to enhance the performance and durability of mortars, with ceramics being a traditional choice. More recently, the addition of nanoparticles has been explored as a means to further improve these properties. However, the effective optimization of the complex interplay between additives in lime-based mortars, which is crucial for enhancing their sustainability, remains an ongoing area of research. This study investigated the effects of red-clay ceramic aggregates (RCC) and nanoparticle-based solutions of Ca(OH)2 and SiO2 on the mineralogy, hydraulicity, surface properties, pore structure, and mechanical properties of lime-based mortars. The addition of nanoparticle-based solutions increased the carbonation reactivity, whereas the ceramic aggregates caused a more extensive conversion of portlandite to calcite on the external faces, indicating reduced porosity during the carbonation process. Pozzolanic reactions and the formation of new calcium silicate compounds were observed, along with improved compaction, smoother surfaces, and microcrack formation. The porosity increased with the addition of the ceramic aggregates, whereas the addition of nanoparticles significantly increased the number of pores in the mesoporous range. The specific surface area of the mortars increased with the inclusion of ceramic aggregates and nanoparticles, whereas the open porosity increased and the density and compressive strength decreased with the addition of nanoparticles and associated pozzolanic reactions that occurred with the inclusion of ceramic aggregates. These findings lay the groundwork for future improvements in the formulation of lime-based mortars to balance hydraulicity, surface characteristics, and mechanical performance while preserving porosity.