Rheological enhancement of high-volume fly ash mixes using ternary mineral blends and chemical additives

Abstract Cement production contributes significantly to global $$\mathrm {CO_2}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>CO</mml:mi> <mml:mn>2</mml:mn> </mml:msub> </mml:math> emissions, creating an urgent need for alternative construction materials. This study proposes a novel ternary mineral-mixed high-volume fly ash (HVFA) system that replaces a significant portion of cement , reducing the reliance on chemical additives and environmental impact. Comparative evaluations were conducted using a commercial viscosity-modifying agent (VMA), sepiolite (SEP), slaked lime (SL), and unslaked lime (UL) as rheology modifiers. A step-by-step mix design assessed the effects of each material on rheological properties, including yield stress, viscosity, and thixotropy. SL and UL improved dynamic and static yield stress with SL showing greater effects. VMA enhanced early-age structural build-up, while SEP exhibited a delayed response, contributing to rheological stability over time. Sensitivity analysis revealed that the combination of SL and VMA mainly influenced the HVFA rheology at early ages. This ternary HVFA system demonstrates the potential to minimize cement consumption and improve fresh-state performance. Graphical Abstract