Hybrid Fly Ash-Based Geopolymeric Foams: Microstructural, Thermal and Mechanical Properties

Area of Science:

• Materials Science
• Chemical Engineering
• Environmental Science

Background:

• Geopolymeric materials offer sustainable alternatives to traditional binders.
• Valorization of industrial byproducts like coal fly ash is crucial for circular economy principles.
• Development of lightweight, high-performance insulating materials is an ongoing challenge.

Purpose of the Study:

• To synthesize novel organic-inorganic geopolymeric foams.
• To characterize the mechanical and thermal properties of these foams.
• To evaluate their potential as low environmental impact materials for thermal insulation.

Main Methods:

• Simultaneous reaction of coal fly ash, alkali silicate solution, and polysiloxane oligomers.
• In situ foaming using elemental silicon (Si⁰) as a blowing agent.
• Density, compressive strength, and thermal conductivity (λ) measurements.

Main Results:

• Successfully prepared geopolymeric foams with densities ranging from 0.3 to 0.7 g/cm³.
• Achieved compressive strength up to approximately 5 MPa at a density of 0.7 g/cm³.
• Obtained thermal conductivity (λ) of 0.145 ± 0.001 W/m·K for a foam with density 0.330 g/cm³, comparable to commercial insulators.

Conclusions:

• The developed geopolymeric foams exhibit promising mechanical and thermal insulation properties.
• Utilizing waste coal fly ash positions these materials as environmentally friendly.
• These foams represent a viable pathway towards sustainable construction and circular economy initiatives.