Why do conventional MAA-MPEG PCEs not work in alkali-activated slag systems?
Yue Zhang, Hsien-Keng Chan, Ziyi Han, Lei Lei
Abstract
This study investigates the correlation between the molecular architecture of methacrylate ester-based polycarboxylate (MPEG PCE) superplasticizers and their influence on the rheological characteristics of alkali-activated slag (AAS). Two variants of MPEG PCE superplasticizers were synthesized utilizing distinct acid monomers (methacrylic acid versus acrylic acid), while maintaining consistent structural parameters for both types. These parameters included the uniform length of the MPEG macromonomer side chain, similar anionicity in the trunk chain, and comparable molecular weights (Mw) of the copolymers. The efficacy of these superplasticizers in AAS binders was assessed through spread flow and rheology testing, and their performance was benchmarked against that in ordinary Portland cement (OPC) pastes. To elucidate the interactions between PCE polymers and AAS binders, this study undertook comparative evaluations encompassing adsorption isotherms, anionic charge densities, solubility, and conformational transformations of calcium complexes for both acrylic acid (AA) and methacrylic acid (MAA) variants.