Mortars with nanosilica and silica fume addition exposed to a sulfate attack

Abstract:

Durability is one of the characteristics to be considered in the concrete structures project, since it is related to the useful life of the buildings. Among the aggressive agents most damaging to concrete are the sulfate ions, which react with the cement hydration products resulting in expansion and cracking of the cementitious matrix. The present work had as objective to evaluate how nanosilica and silica fume influence the mitigation of the sulfate attack, since, due to their filler and pozzolanic effects, they are able to densify the cementitious matrix, reducing the porosity and, consequently, the aggressive agents’ ingress in concrete structures. Therefore, three mortar compositions were evaluated: reference (without additions), 1% nanosilica + 10% silica fume and 10% nanosilica. Compressive strength and water absorption by capillarity tests were performed to characterize the mortars. The sodium sulfate attack was evaluated by means of the dimensional change test, as specified by NBR 13583. The results indicated that the additions use resulted in a raise of compressive strength and in a reduction of the capillary absorption at 28 days, when compared to the reference mortar. However, regarding to durability against sulfate attack, none of the mortars studied showed expansion after 91 days of attack


Reference:
SCHMALZ, Rosana.; LEONI, Vitor L.; ALVES, Rapahel Klein; FERREIRA, Fernanda Giannotti da Silva; QUARCIONI, Valdecir Angelo. Argamassas com adição de nanosílica e sílica ativa expostas ao ataque de sulfatos. In: ENCONTRO LUSO-BRASILEIRO DE DEGRADAÇÃO EM ESTRUTURAS DE CONCRETO ARMADO, 3., 2018, São Carlos. Anais… 15p

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