An Investigation on HVS Paste Modified with Nano- $$\hbox {SiO}_{2}$$ SiO 2 Imperiled to Elevated Temperatures

Abstract

Portland cement (PC) blended with ground granulated blast-furnace slag (denoted as slag) is frequently used to produce more sustainable matrix as well as economical and technical benefits. In this research work, the opportunity of employing $$\hbox {nano-SiO}_{2}$$ (NS) to improve compressive strength of high-volume slag (HVS) paste prior and after exposure to thermal loads has been investigated. PC has been partially replaced with slag at level of 65%, by weight, to produce HVS paste. Then, slag was partially replaced with NS at levels fluctuated from 0.5 to 5%, by weight. After initial curing, specimens were exposed to different thermal loads fluctuated from 200 to 800 $$^{\circ }$$ C with a heating rate of 6.67 $$^{\circ }$$ C/min for 2 h. Compressive strength prior and after heating was tested. The different decomposition phases formed before and after heating were detected with the help of X-ray diffraction and thermogravimetric techniques. The microstructure of the formed hydration products was determined with the help of scanning electron microscopy (SEM). The results illustrated that the compressive strength prior and after firing increased as NS content increased up to 4%, while 5% NS illustrated contradictory results.