Impact of Alkaline Activator and Fly Ash on Strength, Microstructure and Durability Assessment Through Corrosion Resistance of Geopolymer Concrete in the Presence of Chloride Ions

Abstract

To mitigate the problems related to higher energy consumption, higher CO2 emission and disposal of industrial wastes, geopolymer binders based on these industrial waste materials are now widely considered as the promising substitute for Portland cement binders. It may be noted that the production of Portland cement accounts for higher energy consumption and higher amount of CO2 emissions. The geopolymer binder has the potential to produce sustainable concrete. In the present research work, fly ash based geopolymer concrete (GPC) mixes were prepared with different concentrations of NaOH solution i.e., 8 M, 10 M, 12 M, 14 M and 16 M, alkaline solution contents of 190 kg/m3 and 210 kg/m3, sodium silicate solution to sodium hydroxide solution (SS/SH) ratios of 1.5 and 1.75, fly ash particles of different sizes i.e., passing through 150 μm sieve, and 300 μm sieve, and fly ash contents of 425 kg/m3, and 450 kg/m3. Sodium chloride (NaCl) of different concentrations i.e., 1.5%, 3% and 4.5% by mass of geopolymer solids were admixed in GPC mixes during the time of preparation. For compressive strength test, cube specimens of size 150 mm, and for corrosion measurement, prismatic specimens of size 72 mm × 72 mm × 300 mm with a centrally embedded steel bar were prepared from GPC mixes. Slump test on fresh GPC mixes, and compressive strength test on cube specimens at different ages were carried out. To evaluate the corrosion behaviour of rebar in the presence of chloride ions, half-cell potential measurement, and linear polarization resistance measurement for corrosion current density were carried out on prismatic specimens at different ages. The microstructure of GPC was analyzed by carrying out XRD (X-ray diffraction) analysis, FESEM (Field emission scanning electron microscope) analysis and FTIR (Fourier transform infrared) spectroscopy on geopolymer concrete powder samples obtained from cube specimens and prismatic specimens. In addition, free chloride, total chloride and bound chloride content of GPC mixes were determined from the powder samples obtained from cube and prismatic specimens.