Avaliação da atividade pozolânica da sílica nanoestruturada sol-gel e sílica ativa via ensaio de variação de condutividade elétrica

Abstract

Active pozzolanic admixtures are added in concrete to improve some of its properties, such as compressive strength and density. Due to its composition and structure, silica synthetized by sol-gel technique has a great pozzolanic potential. This study evaluated the pozzolanic activity of silica fume and two nanostructured silicas with high specific surface areas, synthetized by sol-gel technique. Electrical conductivity variation measurements were conducted in calcium hydroxide saturated solutions. Results reveal that both nanostructured sol-gel silicas, SN-0 and SN-1, synthetized in this work, have great pozzolanic reactivity. Silicas SN-0 and SN-1 have reacted 35 times and 3,5 times faster than silica fume, respectively. The silicas highest reactivity was observed, especially, in the first few minutes of reaction. Hence, it was verified that both pozzolanicreactivity and reaction kinetics of silica are affected by its specific surface area. Moreover, silica content, test temperature and average pore size also seems to affect silica reactivity. The reaction speed of silicas with average pore size smaller than 6nm or with micropores (~2nm) is reduced over time.