Study on Fly Ash Based Geopolymer Concrete

Geopolymer concrete is a new future construction material which cement is totally replaced by pozzolanic materials like fly ash and activated by highly alkaline solutions to act as a binder in the concrete mix. The use of Portland cement in concrete construction is under critical review due to high amount of carbon dioxide gas released to the atmosphere during the production of cement. In recent years, attempts to increase the utilization of fly ash to partially replace the use of Portland cement in concrete are gathering momentum. Most of this by-product material is currently dumped in landfills, creating a threat to the environment. Fly ash was chosen as the basic material to be activated by the geo polymerization process to be the concrete binder, to totally replace the use of Portland cement. The binder is the only difference to the ordinary Portland cement concrete. The sodium silicate solution's chemical composition was Na2O=15.53%, SiO2=31.87%, and water by mass was 52.6 % and sodium hydroxide solution 10M concentration maintain constant throughout the experiment. Water-to-geopolymer binder ratio of 0.4, alkaline solution-to-fly ash ratio of 0.4 and sodium silicate-to-sodium hydroxide ratio of 2 by mass were �xed 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 speci�ed period of oven heating. The temperature of oven heating was maintained at 60 °C for 24 h duration and tested 7 days after heatingTo activate the Silicon and Aluminium content in fly ash, a combination of sodium hydroxide solution and sodium silicate solution was used Manufacturing process comprising material preparation, mixing, placing, compaction and curing is reported in the thesis. Naphthalene-based superplasticiser was found to be useful to improve the workability of fresh fly ash-based geopolymer concrete, as well as the addition of extra water. The main parameters affecting the compressive strength of hardened fly ash-based geopolymer concrete are the curing temperature and curing time, the molar H2O-to-Na2O ratio, and mixing time.