The impact of nano SiO2 and fluidized catalytic cracking catalysts waste (FCCCw) on cement hydration and physical mechanical properties

Abstract

Nano SiO2 is known to accelerate cement hydration, reduce voids between cement particles and increase the strength. FCCCw also accelerates cement hydration and can increase the strength of hardened cement paste when up to 10% of cement in the mix is replaced by this waste. Our work presents the research into the changes of cement hydration processes and physical and mechanical properties of cement caused by the addition of certain amounts of nano SiO2 and replacement of a portion of cement by FCCCw in the cement mix. The paper presents exothermic peak temperatures, mineral composition, density and compressive strength of cement mixes containing the aforementioned additions. It was found that exothermic peak temperature was reached the fastest in specimens containing nano SiO2 and 5% of FCCCw. The maximum temperature was reached ~4h earlier compared to the control specimen. The binding of cement in specimens containing only FCCCw or only nano SiO2 is slower. X-ray analysis showed that the combination of FCCCw and nano SiO2 increased the amount of calcium hydrosilicates formed. Also, the combined use of FCCCw and nano SiO2 produces higher compressive strength of the specimens compared to the specimens containing only one of the two additions.