Study on the Behaviour of Fly Ash Based Geopolymer Concrete

Geopolymer is a new development in the world of concrete in which cement is replaced by 85% of fly ash with alkaline solutions (NaOH & Na2SiO3) with extra water and superplasticizers. To act as a binder in the concrete mix. M40 grade of concrete used combination cement and fly ash 15% – 85% respectively. For the selection of suitable ingredients of geopolymer concrete to achieve desire strength at required workability, an experimental investigation has been carried out for the gradation of geopolymer concrete and a mix design procedure is proposed on the basis of quantity and fineness of fly ash, quantity of water, grading of fine aggregate, fine to total aggregate ratio. Sodium silicate solution with Na2O = 16.37 %, SiO2 = 34.35 % and H2O = 49.28 % and sodium hydroxide solution having 13M , 10M 15M concentration were obtained throughout the experiment. Water-to-geopolymer binder ratio of 0.40, alkaline solution-to-fly ash ratio of 0.35 and sodium silicate-to-sodium hydroxide ratio of 2.0 by mass were fixed on the basis of workability and cube compressive strength. Workability of geopolymer concrete was measured by flow table apparatus and cubes of 150 mm .side were cast and tested for compressive strength after specified period of oven heating. The temperature of oven heating was maintained at 60 °C for 24 h duration and tested 7 days after heating.