Experimental and microstructural analysis on flyash-GGBS based geopolymer concrete under ambient curing condition

Abstract

The large-scale production of cement is posing environmental problems on one hand and unrestricted depletion of natural resources on the other hand. Each ton of Portland cement production results in loading about one ton of CO2 in to the environment. Environmental and economic reasons require there vision of present concrete making materials. Fortunately within this scenario a new player has emerged that can help in mitigating the problem and the player is Geopolymer Concrete. Hence, the present research work is focused on pozzolanic materials by replacing ordinary Portland cement (OPC) content in the concrete. The pozzolanic materials selected are in the form of geopolymer concrete (GPC) which utilizes waste materials like fly ash, ground granulated blast furnace slag (GGBS), silica fume, etc. Most of the researchers did significant amount of research on fly ash based GPC with heat curing methods. The parameters influencing compressive strength of GPC are total combined aggregate, alkaline to binder ratio, replacement of fly ash with GGBS, mass of sodium silicate to sodium hydroxide, molarity of sodium hydroxide and curing conditions. A total number of 24 cubes of size 150 mm × 150 mm × 150 mm with 14 molarity are prepared, combined total aggregate as 70%, alkaline to binder ratio as 0.30, partial replacement of fly ash with GGBS as 40%, mass of Na2SiO3 to NaOH is 2.5 and admixture as 1.75% mass of binder. The specimens are kept for ambient curing for required days. The mechanical properties are compressive strength test, flexural strength test and split tensile test and the results are 53.10 N/mm2, 4.73 N/mm2 and 4.13 N/mm2 respectively and done the tests on durability properties like absorption, the results is %water absorption 2.865 and the level “Excellent” and done for Sulphate test also. In this research investigation is carried out the mechanical and durability studies and also examine the microstructural behaviour of geopolymer concrete using scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). The existence of geopolymer structure due to the Ca with Ca/Si, Si with Si/Al ratios of 0.63 and 2.4 and the Si/Al ratio (2.4) is greater than the 1.65 indicates the presence of geopolymer products in the composition.