Antimicrobial Activity of Eco-Friendly Fly-Ash-Based Geopolymer Mortar

Area of Science:

• Materials Science
• Civil Engineering
• Environmental Science

Background:

• Ordinary Portland cement (OPC) production is unsustainable due to high CO2 emissions.
• There is a growing demand for eco-friendly construction materials with antimicrobial properties for enhanced durability and occupant health.
• Geopolymer mortars/concretes (GPM/GPC) are emerging as sustainable alternatives to OPC, offering good mechanical and durability characteristics.

Purpose of the Study:

• To investigate the impact of curing temperature on the composition, microstructure, mechanical, and antimicrobial properties of geopolymer mortars.
• To determine the optimal curing temperature for producing GPMs with enhanced strength and antimicrobial activity.
• To evaluate the potential of GPMs as sustainable and hygienic building materials.

Main Methods:

• Geopolymer mortars were produced using low-lime fly ash as a binder and sodium silicate/sodium hydroxide as alkaline activators.
• Samples were cured at various temperatures: 60, 80, 100, and 120 °C.
• Characterization included X-ray fluorescence (XRF) for composition, Scanning Electron Microscopy (SEM) for microstructure, mechanical testing for compressive strength, and the agar diffusion method for antimicrobial activity against bacteria and fungi.

Main Results:

• XRF indicated increased geopolymerization products with higher curing temperatures.
• SEM revealed microstructural cracks in geopolymers cured above 100 °C, leading to reduced mechanical properties.
• The optimal curing temperature of 100 °C yielded the highest compressive strength (48.41 MPa) and significant antimicrobial activity (38.94-49.24 mm inhibition zones).
• Higher alkalinity correlated directly with enhanced antimicrobial efficacy.

Conclusions:

• Geopolymer mortars cured at 100 °C exhibit optimal mechanical strength and potent antimicrobial properties.
• The formation of microstructural cracks at higher curing temperatures negatively impacts mechanical performance.
• GPMs demonstrate significant potential as sustainable building materials, particularly for applications requiring high hygiene standards and resistance to microbial corrosion.