Microstructure Stability and Thermal Resistance of Ash-Based Geopolymer with Sodium Silicate Solution at High Temperature

Current cement-based building materials have a huge disadvantage that they are easily broken due to thermal decomposition at high temperature (over 500°C) of structures of hydrated cement. This is easily observed at construction works when burned, the cement-based mortar and concrete materials and plaster are susceptible to collapse causing damage to buildings or structures. More seriously, these accidents easily cause injuries or loss of life for residents and people working there. Therefore, research on fire resistance and structural stability at high temperatures of building materials is always an interested topic of many scientists. This study utilized resources of highly active alumino silicate materials such as coal bottom ash and rice husk ash to produce geopolymer using sodium silicate solution as an alkaline activator. The ash-based geopolymer has good engineering properties responding to requirements of ASTM C55 and C90 for lightweight concrete brick. It is interesting to note that the geopolymer product was tested for thermal properties at 1000°C such as heat resistance, volumetric shrinkage, mass loss. The experimental results show that the ash-based geopolymer material has high thermal stability with increasing significantly of compressive strength after heated at 1000°C. Moreover, the geopolymer was also carried out to characterize microstructure before and after exposed at high temperature using methods of X-ray diffraction (XRD), scanning electron microscope (SEM). Thermal analysis methods such as thermogravimetric (TG), differential thermal analysis (DTA), and dilatometry-thermal expansion (CTE) were used to evaluate microstructural stability of the geopolymer-based materials.