Geopolymer bricks prepared by MSWI fly ash and other solid wastes: Moulding pressure and curing method optimisation

Area of Science:

• Materials Science
• Civil Engineering
• Environmental Science

Background:

• Geopolymer preparation using solid waste often results in low early strength, hindering engineering applications.
• Optimizing early mechanical properties of geopolymers is crucial for their practical use.
• Red mud-ground granulated blast furnace slag activated by municipal solid waste incineration fly ash and carbide slag (CRMG) is a potential geopolymer precursor.

Purpose of the Study:

• To investigate the impact of moulding pressure and curing methods on the properties of CRMG geopolymer.
• To enhance the early mechanical properties of geopolymer for rapid demoulding applications.

Main Methods:

• Systematic evaluation of compressive strength under varying moulding pressures (up to 30 MPa) and curing conditions (high-temperature, water, and room-temperature curing).
• Microstructural analysis using X-ray Diffraction (XRD), Fourier-Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), and Mercury Intrusion Porosimetry (MIP).
• Synthesis and testing of geopolymer pavement bricks (GPB) under optimized conditions.

Main Results:

• A moulding pressure of 30 MPa increased 3-day compressive strength by 182% and reduced porosity.
• High-temperature (HT) curing boosted 3-day compressive strength by over 130% compared to water or room-temperature curing.
• HT curing promoted the formation of C-(A)-S-H gel, geopolymer gel, and hydrate calcium chloroaluminate (HCC), enhancing structural compactness.

Conclusions:

• Optimized moulding pressure (30 MPa) and HT curing (90°C for 12h) yielded GPB with 54 MPa compressive strength at 3 days.
• The developed geopolymer pavement bricks offer a sustainable and cost-effective alternative to concrete.
• This research provides a foundation for utilizing CRMG in rapid construction projects like unfired bricks.