An experimental investigation on the nano-fly ash preparation and its effects on the performance of self-compacting concrete at normal and elevated temperatures

Abstract

Previous research regarding the performance of self-compacting concrete (SCC) incorporating nano-fly ash (NFA), especially after exposure to elevated temperatures, is scarce. Therefore, this experimental research was conducted to investigate the influence of NFA particles on the performance of SCC at normal and elevated temperatures. The effects of NFA particles were also compared with the influence of fly ash (FA) particles at the same replacement percentages. The experimental program was managed at two stages. At the first stage, the microparticles of FA were transformed into nanoparticles using electric milling process. The size, shape, and consistency of the FA and NFA particles were characterized using scanning electron microscopy. In the second stage, experimental tests were performed to examine the influences of FA and NFA particles on the performance and characteristics of SCC. The investigated parameters included fresh density, dry density, T50 slump flow time, slump flow diameter, elastic modulus, ultrasonic pulse velocity (UPV), and compressive as well as flexural strength. Furthermore, the residual compressive strength, weight loss, and UPV after exposing the concrete samples to 700 °C were also investigated. The results showed that addition of FA and NFA can cause a reduction in the workability as well as flowability of SCC mixtures. On the other hand, the transformation of FA to NFA significantly enhanced the microstructure of the SCC, which led to the enhancement of its mechanical properties and boosted the resistance of the SCC to high temperatures. The outcomes of this study also illustrated that through transforming the particles of FA from microscale to nanoscale, a sustainable and high-performance SCC can be produced.