In this study, geopolymer mortar was produced using Class F fly ash from the thermal power plant in Kutahya Seyitomer (Turkey). The changes caused by the geopolymerization on the properties of the final product were investigated by applying curing on geopolymer mortars in different NaOH concentrations at different temperatures and for different curing times. The purpose of this process was to determine the relationship between alkali solution concentration, curing temperature and curing time. In order to determine the effect of NaOH concentration on geopolymer mortars, three different molarities of NaOH concentrations (3 M, 6 M and 9 M) were used together with sodium silicate (water glass) solution. The samples were cured at two different temperatures (65 and 85 °C). Physical properties such as porosity, bulk density, apparent density and water absorption, and mechanical properties such as flexural strength and compressive strength were determined from the 7-day geopolymer mortar samples after the curing process. As a result, this study determined that curing temperature and curing time had an effect on the physical properties of the geopolymer mortars. It was observed that NaOH concentration had a clear effect on the properties of the mortar cured at 85 °C. Compressive strength values of 21.3 MPa and 22 MPa were obtained from the mortar of 6 M concentration cured at 65 °C for 24 h and from a sample of the same mortar cured at 85 °C, respectively. Compressive strength values of the geopolymer mortars cured at 85 °C increased depending on the curing time and the increase in NaOH concentration. Given the strength values obtained, the optimal thermal curing temperature and the optimal NaOH concentration were 85 °C and 6 M, respectively.

The influence of the NaOH solution on the properties of the fly ash-based geopolymer mortar cured at different temperatures

Effect of mechanical activation of fly ash on the properties of geopolymer cured at ambient temperature

Due to their good performance and environmental friendliness, fly ash-based construction materials have great potential as alternatives to ordinary Portland cement. To realize sustainable development and beneficial use of fly ash in the construction industry, this paper presents a comprehensive review of relevant literature to evaluate the properties and performance of fly ash, with a particular focus on recent advances in characterization, compositional understanding, hydration mechanism, activation approaches, durability and sustainability of fly ash as a construction material. Several key aspects governing the performance of fly ash, including chemical composition, activator type and hydrates evolution in concrete, are highlighted. Finally, the important needs, pertinent to the optimal and broad utilization of fly ash as an integral part of sustainable construction materials, are identified for further research and development, where large-scale application studies, further classification of fly ash, advanced characterization tools and technology transfer to biomass fly ash are recommended.

Characteristics and applications of fly ash as a sustainable construction material: A state-of-the-art review

Progressive utilisation prospects of coal fly ash: A review

Recycling phosphogypsum and construction demolition waste for cemented paste backfill and its environmental impact

Synthesis of geopolymer composites from blends of CFBC fly and bottom ashes

Enhanced adsorption of bromate from aqueous solutions on ordered mesoporous Mg-Al layered double hydroxides (LDHs).

Utilization of fly ash coming from a CFBC boiler co-firing coal and petroleum coke in Portland cement

The physical–chemical characteristics of mechanically-treated circulating fluidized bed combustion (CFBC) fly ash, such as 45 μm sieve residue, granulometric distribution, water requirement, specific gravity, pH value, and mineralogical phases, were investigated. It was found that the grinding process can be divided into three stages. The increase in fineness of ground CFBC fly ash is very sharp in the first stage, then slows down in the second stage, and in the last stage it becomes almost invary. The water requirement decreases with prolonged grinding time, and slightly increases during the last stage of grinding. Ground CFBC fly ash shows a higher specific gravity due to the crushing of coarse particles and carbon particles. The pH of ground CFBC fly ash is greater than that of the original CFBC fly ash, indicating that ground samples react more rapidly with water. The mineralogical compositions remain unchanged with grinding, although the intensity of the crystalline phases decreases and the half peak width increases.

Feihu Li

Papers

Synthesis of geopolymer composites from blends of CFBC fly and bottom ashes

Enhanced adsorption of bromate from aqueous solutions on ordered mesoporous Mg-Al layered double hydroxides (LDHs).

Utilization of fly ash coming from a CFBC boiler co-firing coal and petroleum coke in Portland cement

The physical–chemical characterization of mechanically-treated CFBC fly ash

Self-cementitious properties of fly ashes from CFBC boilers co-firing coal and high-sulphur petroleum coke