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

Area of Science:

• Materials Science
• Chemical Engineering
• Environmental Science

Background:

• Circulating fluidized bed combustion fly ashes (CFAs) are typically low-reactivity materials.
• Geopolymer synthesis offers a potential route for valorizing industrial byproducts like CFAs.
• Enhancing the reactivity of low-grade source materials is crucial for successful geopolymerization.

Purpose of the Study:

• To investigate the feasibility of using low-reactivity CFAs as a source material for geopolymer synthesis.
• To enhance the reactivity of CFAs through an alkali fusion process.
• To characterize the resulting geopolymer products and assess their potential.

Main Methods:

• Alkali fusion process to increase Si and Al dissolution from CFAs.
• Dissolution tests in sodium hydroxide solutions to evaluate CFA and metakaolin (MK) reactivity.
• Alkali activation of source materials using sodium silicate solution.
• Characterization using mechanical testing, SEM, XRD, and FTIR.

Main Results:

• Alkali fusion significantly enhanced the reactivity of low-reactive CFAs.
• Geopolymer samples were successfully synthesized using alkali-fused CFAs.
• Balancing the Na/Al ratio with metakaolin improved geopolymer properties.
• Characterization confirmed the formation of geopolymer structures.

Conclusions:

• Low-reactivity CFAs can be effectively recycled for geopolymer production via alkali fusion.
• This method offers a sustainable approach to utilize industrial waste materials.
• Optimized alkali activation and source material blending are key for successful geopolymerization.