Alkali-Activated Binary Binders with Carbonate-Rich Illitic Clay.

Area of Science:

• Materials Science
• Geochemistry
• Sustainable Construction

Background:

• Investigating alternative binders to reduce Portland cement usage.
• Utilizing industrial by-products like blast furnace slag and fly ash in binder production.
• Exploring the potential of carbonate-rich illitic clay as a precursor for alkaline binders.

Purpose of the Study:

• To evaluate alkaline binders derived from binary mixtures of illitic clay and industrial by-products.
• To assess the impact of blast furnace slag and fly ash on binder properties.
• To determine the mechanical strength and microstructural characteristics of activated pastes.

Main Methods:

• Pre-treatment of illitic clay by grinding and heating to 700 °C.
• Alkali activation of binary mixtures using NaOH solutions (4 M and 8 M).
• Characterization using heat flow calorimetry, compressive strength tests, X-ray powder diffraction (XRPD), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDX).

Main Results:

• The primary reaction product was identified as C-A-S-H/(N, C)-A-S-H type gel.
• A 1:1 mixture of illitic clay and blast furnace slag yielded a compact matrix with a 28-day compressive strength of 45 MPa.
• The illitic clay/fly ash blend exhibited lower compressive strength (<15 MPa) due to fly ash's limited reactivity at room temperature.

Conclusions:

• Binary mixtures of illitic clay and blast furnace slag can form highly performant alkaline binders.
• The interaction between calcium-rich precursors is crucial for matrix development and mechanical strength.
• The studied clay activation method is scalable for industrial applications, offering a sustainable alternative binder option.