In this study, the effect of silicon dioxide nano particle and fly-ash on the permeability of sand were investigated. For this purpose, various combinations of fly ash and sand were investigated to examine the impact of mixing of fly with sand. We can make a least permeable mass by mixing 80% of fly ash with 20% sand. According to specific gravity of sand, fly ash, nano silica and weight of the mould with a porosity of 0.4 these materials has been mixed manually. Fly ash is mixed with the fine sand in increasing proportions of 5%, 15%, 25%, 35%, 45%, 55%, 65%, 75%, 85%, 100%. According to the results of present study, 80% fly ash mixed with 20% sand provides the least permeable combination compared to the rest. The percentage-mix of fly ash and sand is taken different from previous study but least combination was achieved with a similar combination of 80% fly ash and 20% sand which was also reported by Gupta and Alam 2004. To make the least permeable sample to almost impermeable, nano silica mixed with least permeable sample in increasing percentage by 5%, 7.5%, 10% and 12.5%. A falling head and constant head method was used to test all samples for hydraulic conductivity.
Results of present study revealed that when 20% of sand mixed with 80% of fly ash gives value of permeability (6 × 10-05 cm/s) which are 86 times lower than the permeability of sand.
It was observed that a mixture of 20% sand and 80% fly ash mixed with 12.5% of nano silica gives a permeability (2.20 × 10-06 cm/s) i.e in the range of clay which is 2340 times lower than the permeability of sand.
The permeability property was found to be highly improved on addition of fly ash and nano particles to sand.
Comprehensive results proving the improvement in the permeability properties have been obtained in the specimen containing 12.5% nano silica with least permeable sample of fly ash–sand mixture.
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