Abstract
In this study, the strength reduction of high-strength concrete (HSC) integrating silica fume (SF) and nano-silica (NS) exposed to elevated temperatures besides its mass loss is evaluated. Cubes and cylinders were cast and tested at 28 and 56 d to evaluate the concrete compressive and tensile strengths (f(cu) and f(tu)), respectively. The prepared cubes and cylinders were subjected to elevated temperatures (T = 200, 400, 600, 800, and 1000 degrees C), cooled in air, and tested in compression and tension, respectively. For the cement paste and aggregate, spot analysis was performed through scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). Furthermore, SEM between aggregate and cement paste was performed. The obtained results indicated that for concrete mixes incorporating NS, compressive strength increased as temperature was raised to 400 degrees C and decreased as temperature increased from 400 to 800 degrees C. In addition, a remarkable reduction in the concrete tensile strength was observed up to T = 800 degrees C. At T = 1000 degrees C, all specimens were destroyed. Moreover, the lowest Ca/Si ratio was observed for the NS mixes according to the EDS spot analysis results. The mass loss of the concrete mixes integrating SF was higher than that of the mixes integrating both SF and NS except at 800 degrees C. Finally, a detailed review of the effect of macro and nanomaterials on the concrete properties was presented.