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

Abstract

This paper shows results of laboratory study on the effects of nano-SiO2 on Portland cement-fly ash systems. It is aimedto improve performance of fly ash–cement systems, particularly at early age, with the inclusion of nano-SiO2. In order toobserve the effects of nano-SiO2 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-SiO2 by weight of blended cements. Workability,setting time, water absorption capacity, fire resistance, compressive strength and isothermal calorimeter tests were conductedon the cementitious systems. The results indicate that increasing quantity of fly ash increased workability, setting time, waterabsorption capacity of cementitious systems, whereas the increasing quantity of nano-SiO2 reduced these values. Significantincrement in compressive strength were observed, especially at early ages of fly ash–cement systems with nano-SiO2 addition,compared to fly ash added systems, which may compensate for the decrease in compressive strength caused by fly ash. NanoSiO2 addition accelerated hydration reactions at early age. By partially eliminating the negative effects of fly ash withnano-SiO2, high rates of fly ash can be used in cementitious systems, thus forming more sustainable systems.</p