Effect of water addition, plasticizer and alkaline solution constitution on fly ash based geopolymer concrete performance

Using fly ash based geopolymer concrete (GPC) instead of portland cement concrete, partially or totally, can reduce CO2 emissions released during OPC production, which requires burning large quantities of fuel result in significant CO2 emissions. Development of GPC became a major concern to widen its usage. This paper is a study of the influence of additional water content, plasticizer content, sodium hydroxide solution molarity, alkaline solution to fly ash ratio and sodium hydroxide to sodium silicate ratio on fly ash based GPC. The studied properties of fly ash based GPC was workability, compressive strength, splitting tensile strength, modulus of elasticity, absorption, and porosity. The results showed that, generally, increasing additional water content increased workability, but decreased other fly ash based GPC properties and the optimum additional water content was found to be 30 kg/m3 which has slight effect on geopolymer properties. The increase of plasticizer content up to 10.5 kg/m3 had acceptable effects on GPC properties due to improved workability. The optimum molarity of sodium hydroxide solution was found to be 16 M. GPC properties was significantly affected by alkaline solution to fly ash ratio and 0.40 was expected to be the optimum ratio. Increasing sodium hydroxide solution to sodium silicate solution ratio reduces geopolymer concrete properties; nevertheless, low ratio is not economic due to sodium silicate solution cost.