Low Carbon Alkali-Activated Slag Binder and Its Interaction with Polycarboxylate Superplasticizer: Importance of Microstructural Design of the PCEs
Ran Li, Wolfgang Eisenreich, Lei Lei, Johann Plank
Abstract
To investigate the role of polycarboxylate superplasticizers in a low carbon alkali-activated slag (AAS) system, two series of APEG and HPEG polycarboxylate ethers (PCEs) with different anionicities were designed and synthesized in this study. The resulting PCE samples were characterized via size exclusion chromatography, anionic charge titration, and high-resolution 13C NMR spectroscopy. The paste and mortar spread flow tests suggest that in AAS, the synthesized HPEG PCEs exhibit superior dispersing performance over the APEG PCEs, especially at high anionicity. Based on the spread flow tests and adsorption measurements, it became apparent that the dispersing power of the PCEs increases with their anionicity as a result of stronger adsorption on slag. Furthermore, 13C NMR spectroscopy was utilized to identify specific structural motifs in the architecture of the PCE copolymers. It was found that HPEG PCEs possessing AAA and AAE as dominant monomer sequences represent preferable molecular structures compared to APEG PCEs holding EAE as their main monomer sequence. The study confirms the pivotal role of specific molecular design for effective PCE superplasticizers.