Influence of Nanosilica and Ground Granulated Blast Furnace Slag on Mechanical and Durability Properties of Blended Concrete over Varied Fire Durations

Abstract

This study explores the effect of nanosilica (NS) and ground granulated blast furnace slag (GGBFS) in varied quantities (0%–5% NS and 0%–25% GGBFS) on the postfire mechanical and endurance characteristics of concrete at temperatures ranging from 200°C to 1,000°C. To examine bonding performance and structural endurance, a full range of experimental evaluations was methodically carried out, including bond strength evaluations, rapid chloride permeability, chloride attack tests, and water penetration testing. Advanced methods like scanning electron microscopy and X-ray diffraction were used to examine the postfire internal structure. The combination of NS and GGBFS in concrete compositions resulted in noticeable improvements in mechanical resilience and endurance. This was evident by increased bond strength (a notable 12% rise with 4% NS and 20% GGBFS), decreased chloride permeation (a significant 26% drop), and decreased water penetration (about 20% reduction). Interestingly, this optimum concrete mix performed well even at high temperatures, with modest performance improvements at 200°C–400°C but apparent structural deterioration at greater temperature levels. Nonetheless, the composite concrete was demonstrated to perform well at higher temperatures in contrast with control samples. Further, this research develops a reliable correlation for forecasting concrete performance under high heat circumstances as well as providing essential insights critical for the precise design of concrete buildings in extreme situations.