Effect of Nano-SiO2 on Strength and Hydration Characteristics of Ternary Cementitious Systems

This paper shows results of laboratory study on the effects of nano-SiO 2 on Portland cement-fly ash systems. It is aimed to improve performance of fly ash–cement systems, particularly at early age, with the inclusion of nano-SiO 2 . In order to observe the effects of nano-SiO 2 particles on the strength and hydration kinetics of fly ash blended cementitious systems, binary and ternary systems were prepared by adding 0.25–1.5% nano-SiO 2 by weight of blended cements. Workability, setting time, water absorption capacity, fire resistance, compressive strength and isothermal calorimeter tests were conducted on the cementitious systems. The results indicate that increasing quantity of fly ash increased workability, setting time, water absorption capacity of cementitious systems, whereas the increasing quantity of nano-SiO 2 reduced these values. Significant increment in compressive strength were observed, especially at early ages of fly ash–cement systems with nano-SiO 2 addition, compared to fly ash added systems, which may compensate for the decrease in compressive strength caused by fly ash. Nano-SiO 2 addition accelerated hydration reactions at early age. By partially eliminating the negative effects of fly ash with nano-SiO 2 , high rates of fly ash can be used in cementitious systems, thus forming more sustainable systems.