Strength studies on geopolymer concrete with GGBS and Fly ash

Abstract

Geopolymer concrete is a pollution controlled and eco-friendly alternate material used for construction in the recent years. This concrete has many advantages and applications. The main aim of this study is to check the effect of Fly ash and Ground Granulated Blast Furnace Slag (GGBS) on the mechanical properties of Geopolymer concrete at different replacement levels of GGBS by fly ash from 0 to 25% with 5% variation. From previous researches on Geopolymer concrete, an optimized mix is identified for testing mechanical behaviour. Sodium silicate (Na₂SiO₃) and sodium hydroxide (NaOH) of 12 Molarity is used as activator solution in the ratio of 1:2.5. A carboxylic based admixture called La Hypercrete S25 is added in the mix by 1% of the weight of GGBS for increasing the workability of Geopolymer concrete. Cubes of 100mm size are cast for determining the compression strength behavior. Cylinders of 100mm dia and 200mm height are cast for splitting tensile strength and beams of size 500mm length with 100mm x 100mm cross section are cast for flexural strength. The specimens are cured at ambient temperature and tested on 7 and 28 days. The test result shows the strengths gradually increases for 5, 10, 15 and 20% replacement of GGBS by fly ash. The maximum values are obtained for 20% of GGBS replacement by flyash in all the tests. The strengths reduce for replacements of above 20%. This study concludes that geopolymer concrete performs well in strength properties with GGBS and Fly ash.