This study investigates the combined effects of multi-walled carbon nanotubes (MWCNT) and silica fume on the workability, microstructure, thermal stability, and compressive strength of concrete. The addition of these admixtures slightly reduced slump performance due to their reinforcing effect. However, the concrete remained within the medium workability range. Scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS) confirmed the successful integration of MWCNT and silica fume. The analysis revealed improved matrix densification and stronger interfacial bonding. Thermogravimetric analysis (TGA) and Fourier transform infrared (FTIR) spectroscopy provided further insights into the material’s thermal stability and chemical interactions. These microstructural and thermal improvements contributed to a 31.5% increase in compressive strength compared to the control mix. The findings highlight the synergistic role of MWCNT and silica fume in enhancing concrete performance.

Hybrid hydrophobic coatings (HHCs), which combine organic and inorganic materials, have demonstrated superior weathering resistance compared to conventional organic coatings in conserving stone heritage structures. Among the inorganic components of HHCs, nanosilica is especially promising because of its ability to form durable, weathering-resistant and hydrophobic silane-based structures. This overview examined recent studies, advances, and emerging trends about nanosilica-based HHCs from 2020 to 2024 using the “Boolean strategy” and search terms “stone”, “heritage”, “hydrophobic”, and “coating”, capturing 5244 articles. After screening for titles containing “nanosilica” (470 items remained), excluding works related to “consolidants” and “cement” (171 items remained), and requiring quantitative data on formulations, methods, and performance of nanosilica-based HHCs in stone heritage structures, 16 relevant works were identified. China and Italy dominated research works on nanosilica-based HHC development, which was applied to stone heritage structures composed of carbonate materials (e.g., limestone, dolomite, and Palazzolo carbonates) and silica-rich materials (e.g., Qingshi stone, Hedishi stone, and red sandstone). Key evaluation metrics reported by multiple authors to evaluate HHC efficacy included water contact angle (WCA), total color difference (TCD), and solution pH. Moreover, ultraviolet light (UV) durability, thermomechanical stability, biocidal efficiency, and graffiti protection were achieved when nanosilica was combined with other nanomaterials. Integrating emerging technologies, such as artificial intelligence (AI), internet-of-things (IoT), and smartphones with colorimeter apps could improve accessibility, real-time monitoring and reliability of HHC testing, while adherence to standardized testing protocols would further enhance comparability and practical application across studies. Overall, this overview provides valuable insights into nanosilica-based HHCs for researchers and restorers/conservators of stone heritage structures.