Parameter optimization for fly ash geopolymer mixtures: molarity, silica modulus, and solution/binder influence.

Area of Science:

• Materials Science
• Civil Engineering
• Environmental Science

Background:

• Portland cement production has significant environmental drawbacks, including high energy use, resource depletion, and CO₂ emissions.
• Geopolymers derived from fly ash offer a sustainable alternative with reduced environmental impact and good mechanical properties.

Purpose of the Study:

• To develop and validate a simple dosage methodology for fly ash-based geopolymers.
• To establish correlations between key compositional parameters and geopolymer compressive strength.
• To provide a framework for optimizing geopolymer mix design for consistent performance.

Main Methods:

• Formulation of geopolymer mixtures using fly ash as a precursor.
• Systematic variation of water-to-binder (w/b), aggregate-to-binder (m), alkaline solution molarity (M), and silica modulus (Ms).
• Curing of samples at 25°C and 60°C, followed by compressive strength testing.
• Validation using isothermal calorimetry, X-ray diffraction (XRD), and scanning electron microscopy (SEM).

Main Results:

• Strong linear correlation (R²=0.9952) between compressive strength and w/b ratio.
• Quadratic relationship (R²=0.9927) observed between compressive strength and aggregate/binder ratio.
• Significant enhancement in mechanical performance with thermal curing (60°C).
• Experimental compressive strength reached 50.19 MPa, with a predictive model achieving 46.99 MPa (6.3% error).
• XRD and SEM confirmed sodalite phase formation, indicating successful geopolymerization.

Conclusions:

• The proposed dosage methodology is effective for optimizing fly ash-based geopolymer formulations.
• The methodology provides a reliable framework for predicting mechanical performance.
• This research advances the development of sustainable construction materials with predictable and consistent properties.