Improving Workability of Alkali‐Activated Slag Pastes With Novel Linear Copolymer Superplasticizers

ABSTRACT The demand for sustainable construction materials facilitates the development of alkali‐activated slag (AAS) as an alternative cementitious material to cement, while the poor workability of AAS is one of the key problems limiting its practical applications. This study systematically investigates the structure‐performance relationships of poly(acrylic acid‐ co ‐2‐acrylamido‐2‐methylpropanesulfonic acid) (AA‐ co ‐AMPS, PAS) copolymers as superplasticizers for AAS systems. Two model PASs with distinct monomer ratios (AA:AMPS = 0.1 and 15) are synthesized and characterized. PAS15, with higher carboxyl group density and charge density, demonstrates superior dispersion efficiency and fluidity retention in moderate‐alkalinity systems (4 wt% Na 2 O) attributed to enhanced adsorption and Ca 2+ chelation. Conversely, PAS0.1, enriched in hydrophobic AMPS units, outperforms PAS15 under high alkalinity (8 wt% Na 2 O) due to alkaline‐induced aggregation on particle surface providing steric stabilization. In situ calorimetry and 1 H LF‐NMR reveal PAS15's stronger retardation effect on alkali‐activated reaction, extending induction period and delaying gel formation. Pore solution analysis confirms PAS15's ability to suppress slag dissolution and Ca 2+ consumption by gel formation, contributing to the prolonged fluidity retention. Both copolymers preserve early‐age compressive strength, demonstrating compatibility with AAS mechanical development. This work establishes a molecular design framework for the superplasticizers tailored for AAS, balancing electrostatic repulsion, steric hindrance, and chelation effects to address the challenges in dispersing AAS.