Mechanical and Microstructural Characteristics of Ambient Cured Fly Ash-Based Geopolymer Materials

Aluminosilicate source powder and various alkaline solutions can be combined to produce three-dimensional eco-friendly materials known as geopolymers. Due to the presence of amorphous aluminosilicate phases, fly ash powder, a byproduct of a thermal power plant, has the potential to serve as a raw material for geopolymer synthesis. In this current investigation, geopolymers are prepared by alkali activation of fly ash powder with an alkaline solution. Geopolymer samples were synthesized using class F fly ash powder and a combination of 14 molar sodium hydroxide (NaOH) solutions and sodium silicate (Na2SiO3) solutions, followed by ambient curing. After curing, the mechanical properties, such as compressive strength, are determined. The specimen of geopolymer that has undergone a 390-day ambient curing process has the maximum compressive strength, flexural strength, and micro-hardness value of 89.47 MPa, 15.8 MPa, and 171.21 HV, respectively. To confirm mechanical properties data, tested samples were further analyzed by field emission scanning electron microscopy (FESEM) equipped with energy-dispersive X-ray spectroscopy (EDS), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR), respectively. Further, to test the durability, a water absorption test was conducted where the immersion days were 7, 14, and 28 days, respectively. The lowest water absorption was 5.70% after exposure for 28 days.