Fly ash-based geopolymer: clean production, properties and applications

Production of bricks from waste materials – A review

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

This paper presents an investigation of the compressive strength and the durability of lignite bottom ash geopolymer mortars in 3% sulfuric acid and 5% sodium sulfate solutions. Three finenesses of ground bottom ash viz., fine, medium and coarse bottom ash were used to make geopolymer mortars. Sodium silicate, sodium hydroxide and curing temperature of 75 °C for 48 h were used to activate the geopolymerization. The results were compared to those of Portland cement and high volume fly ash mortars. It was found that the fine bottom ash was more reactive and gave geopolymer mortars with higher compressive strengths than those of the coarser fly ashes. All bottom ash geopolymer mortars were less susceptible to the attack by sodium sulfate and sulfuric acid solutions than the traditional Portland cement mortars.

Resistance of lignite bottom ash geopolymer mortar to sulfate and sulfuric acid attack

Study on solids-to-liquid and alkaline activator ratios on kaolin-based geopolymers

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

Low-reactive circulating fluidized bed combustion (CFBC) fly ashes as source material for geopolymer synthesis

Synthesis of thermostable geopolymer from circulating fluidized bed combustion (CFBC) bottom ashes.

This paper presents a study on geopolymer bricks manufactured using bottom ash from circulating fluidized bed combustion (CFBC). The alkali activators used for synthesis were sodium silicate, sodium hydroxide, and potassium hydroxide and lithium hydroxide solutions. The study included the impact of alkali activator on compressive strength. The reaction products were analysed by XRD, FT-IR and SEM/EDS. The compressive strength of bricks was dependent on the modulus of the sodium silicate activator and the type and concentration of alkali activator. The highest compressive strength could be gained when the modulus was 1.5, and the value could reach 16.1 MPa (7 d after manufacture) and 21.9 MPa (28 d after manufacture). Under pure alkaline systems, the compressive strength was in the order of 10 M KOH>10 M NaOH>5 M LiOH>5 M KOH>5 M NaOH. Quartz was the only crystalline phase in the original bottom ash, and no new crystalline phase was found after the reaction. The main product of reaction was amorphous alkal...

Feasibility of manufacturing geopolymer bricks using circulating fluidized bed combustion bottom ash

The invention discloses a method for preparing fly ash-based geopolymer aerated concrete, which comprises the following steps of: mixing fly ash with solution of sodium silicate in a certain ratio, and stirring uniformly; and adding a certain amount of metal aluminum powder, and continuing to stir until slurry is foamed and hardened to obtain the fly ash-based geopolymer aerated concrete. The method has the advantages of simple process, high mechanical strength of products, high utilization rate of the fly ash, effective environmental protection, capability of meeting requirements of few inorganic heat insulating materials on the market, and obvious economic, environmental and social benefits.

Lifeng Shen

Papers

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

Low-reactive circulating fluidized bed combustion (CFBC) fly ashes as source material for geopolymer synthesis

Synthesis of thermostable geopolymer from circulating fluidized bed combustion (CFBC) bottom ashes.

Feasibility of manufacturing geopolymer bricks using circulating fluidized bed combustion bottom ash

Method for preparing fly ash-based geopolymer aerated concrete