Abstract
In this paper, the effect on thermal behavior and compounds mineralogy of replacing different percentages of fly ash with compact particles was studied. A total of 30% of fly ash was replaced with mass powder glass (PG), 70% with mass natural aggregates (S), and 85% with mass PG and S. According to this study, the obtained fly ash based geopolymer exhibits a 20% mass loss in the 25–300 °C temperature range due to the free or physically bound water removal. However, the mass loss is closely related to the particle percentage. Multiple endothermic peaks exhibit the dihydroxylation of β-FeOOH (goethite) at close to 320 °C, the Ca(OH)2 (Portlandite) transformation to CaCO3 (calcite) occurs at close to 490 °C, and Al(OH)3 decomposition occurs at close to 570 °C. Moreover, above 600 °C, the curves show only very small peaks which may correspond to Ti or Mg hydroxides decomposition. Also, the X-ray diffraction (XRD) pattern confirms the presence of sodalite after fly ash alkaline activation, whose content highly depends on the compact particles percentage. These results highlight the thermal stability of geopolymers in the 25–1000 °C temperature range through the use of thermogravimetric analysis, differential thermal analysis, and XRD.
Highlights
In recent years, strong technological development, the population increase, and the rapid development of the house-building industry in particular have led to a large lack of housing areas and to high demand for building materials
The X-ray diffraction (XRD) pattern confirms the presence of sodalite after fly ash alkaline activation, whose content highly depends on the compact particles percentage
The Thermogravimetry-Differential Thermal Analysis (TG-Differential thermal analysis (DTA)) simultaneous thermal analysis was used to evaluate the thermal stability of geopolymers after replacing high percentages of fly ash with two types of particles
Summary
Strong technological development, the population increase, and the rapid development of the house-building industry in particular have led to a large lack of housing areas and to high demand for building materials. Geopolymers are inorganic materials, based on silica-alumina, which are chemically balanced by Group I oxides [2]. A geopolymer, resulting from the exothermic process involving oligomers, is a very long reticular polymer with silicon groups (SiO4 ) and a specific tetragonal network of aluminum oxide (AlO4 ) [4]. The bonds between these tetragons are balanced by alkaline ions of K+ , Na+ , or Li+ [4]. Any geopolymer can be divided into two main constituents: the base material and the Materials 2020, 13, 343; doi:10.3390/ma13020343 www.mdpi.com/journal/materials
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