Effect of nano-SiO2, nano-Al2O3 and nano-Fe2O3 powders on compressive strengths and capillary water absorption of cement mortar containing fly ash: A comparative study

In this study, addition of both nano-SiO2 (NS), nano-Al2O3 (NA) and nano-Fe2O3 (NF) powders and their binary and ternary combinations on the compressive strength and capillary water absorption of cement mortars containing fly ash (FA) were investigated. Powder amounts were used at ratios corresponding to 0.5 wt%, 1.25 wt% and 2.5 wt% of the binder for all mixtures. Results show that addition of any single type of oxide powders at 1.25% increased compressive strength of the mortars much further than the other proportions. The use of NS + NA powders at 1.25% improved the compressive strength by the most compared to the control specimen. For all binary powder combinations, the rate of increase in strength reached generally their peak on the 28th day and gradually decreased through aging. Among all groups, the best results were obtained from the mortars added with NS + NA + NF powders at 1.25%. For this particular mortar, 7-32% increase in the compressive strength and 14% decrease in the capillary absorption were determined relative to the control specimen. Agglomeration formation due to excessive use of nano powders and their pozzolanic activity should be investigated in detail. The results were also compared with those obtained from Oltulu and Sahin (2011). (C) 2013 Elsevier B.V. All rights reserved.