Rice-Husk-Ash-Based Geopolymer Coating: Fire-Retardant, Optimize Composition, Microstructural, Thermal and Element...

Area of Science:

• Materials Science
• Chemical Engineering
• Construction Technology

Background:

• Geopolymers from fly ash, metakaolin, and slag show good fire resistance.
• Limited research exists on rice husk ash (RHA) geopolymer coatings' fire and thermal properties.
• Previous studies often used inefficient one-factor-at-a-time (OFAT) methods.

Purpose of the Study:

• To investigate the impact of RHA/activated alkaline solution (AA) ratio and NaOH concentration on RHA-based geopolymer coating properties.
• To determine the optimal composition for fire-retardant and thermal performance.
• To analyze the microstructure and elemental characteristics of the RHA-based geopolymer coating.

Main Methods:

• Response Surface Methodology (RSM) for experimental design and analysis.
• Preparation of RHA by burning rice husk at ~600 °C for 24 hours.
• Evaluation using fire-retardant tests, TGA, XRD, DSC, CTE, and SEM.

Main Results:

• RHA/AA ratio significantly influenced temperature at equilibrium (TAE) and time to reach 300 °C (TT300).
• Optimal TAE and TT300 achieved with RHA/AA ratio of 0.30 and 6 M NaOH.
• SEM revealed a dense geopolymer gel with a glassy appearance and thin needles upon firing, indicating good fire resistance.

Conclusions:

• RHA is a promising aluminosilicate source for geopolymer coatings.
• The optimized RHA-based geopolymer coating exhibits high insulating capacity, low thermal expansion, and minimal cracking.
• These coatings can enhance fire safety in residential and commercial buildings.