Use of Construction Waste with Nano-Silica Extracted from Rice Husk in Concrete Production

Abstract

The use of construction and demolition waste (CDW) as recycled aggregates in concrete made from rice husk-based nano-silica is examined. In this research, rice husk ash (RHA) in nano-silica form was used as partial replacement for cement. Silica oxide was extracted and purified by dissolving RHA in sodium hydroxide solution at 100oC for four hours. The filtrate of the mixture was titrated with 10 % H2SO4 thereby producing silica oxide precipitate. This precipitate was characterized and found to contain 95.5 % SiO2 and 4.5 % of other impurities. The silica oxide precipitate was grinded to nano particle size and characterized. Experimental results show that: 4% of cement content can be replaced with RHA nano-silica and can be used together with 25 % natural aggregate being replaced with construction waste to produce concrete of equivalent compressive strength to that of 100 % natural aggregate. While the compressive strength of concrete made with only recycled aggregate is very low compared with that of natural aggregate. It was recommended that 4 % nano-silica ash and 25 % recycled wastes be used as partial replacement of cement and natural aggregates respectively.