Abstract: The present disclosure provides a method of preparing a composition of a cold setting geo-polymer based building material. The cold-setting geo-polymer concrete is a green concrete that requires curing at ambient conditions. The method includes mixing one or more aggregates and a plurality of chemical ingredients in a mixing apparatus, and chemically activating an obtained geo-polymer concrete mix by adding an alkaline activator. The one or more aggregates include a plurality of stone chips and a plurality of sand particles. The plurality of chemical ingredients includes a fly ash and a calcium hydroxide solution. The fly ash includes one or more alumino-silicate aggregates. The fly ash, the plurality of sand particles and the calcium hydroxide solution, and the plurality of stone chips are mixed in a first pre-determined ratio. The alkaline activator prevents temperature curing of the cold-setting geo-polymer concrete.