Mechanical and Thermal Properties of Fly Ash-based Geopolymer Cement

The geopolymer concrete is a more durable and green material with less CO2 emission and less energy consuming as compared with the widely used Portland cement (PC) concrete. In this thesis, an experimental study of the thermo-mechanical properties of a cement prepared using a class F fly ash and three different alkali-activators (NaOH activator, NaOH and Na2SiO3 mixture activator, and KOH and Na2SiO3 mixture activator) is presented. The mechanical properties, including the compressive strength, shrinkage, weight loss, and chemical composition, are investigated utilizing several key tools, such as X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and Energy Dispersive X-ray Spectroscopy (EDXS) measurements. The effects of the water/ash ratio, curing methods, cooling methods, and sealing degree on the compressive strength and thermal properties of the geopolymer products are studied and analyzed in details. The tested results show that the geopolymer cement cured at appropriate conditions can reach a compressive strength of more than 100MPa and it also has an excellent heat resistance with a remarkable strength after the 500oC heating. In addition, it is found that the studied geopolymer cement possesses a much higher spallation resistance when suddenly cooled down by water after the high temperature heating than the ordinary Portland cement concrete which has a high spallation tendency. These findings indicate that the geopolymer cement may be an excellent construction material for the fire-protection and fire-prone structures