Effect of alkali activator dosage on compressive and tensile strength of ground granulated blast furnace slag based geopolymer concrete

Abstract

Use of ordinary portland cement contributes to environmental deterioration by releasing enormous quantities of CO2. To reduce use of cement, this research focuses on preparation of solely ground granulated blast-furnace-slag-based geopolymer binder, activated by a combination of sodium hydroxide and sodium metasilicate cured under ambient temperature at 27 °C. Engineering properties of geopolymer binder are evaluated and compared with conventional cement to assess its suitability as a binder for making geopolymer concrete. Compressive strength, flexure strength, and split tensile strength are determined for geopolymer concrete. Microstructural analysis of geopolymer is performed by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM) with energy dispersive X-ray analysis (EDAX), and Fourier-transform infrared spectroscopy (FTIR) tests. The concentration of alkali activators is optimized by laboratory trials and maximum compressive, flexural, and split tensile strengths of 44.07, 5.60, and 4.39 MPa, respectively, are obtained for geopolymer concrete at 2 mol/L concentration of sodium hydroxide solution with the ratio of sodium metasilicate to sodium hydroxide taken as 2.0.