Preparation of isoprenol ether-based polycarboxylate superplasticizers with exceptional dispersing power in alkali-activated slag: Comparison with ordinary Portland cement

摘要

For this study, a series of isoprenol ether (IPEG) based PCE superplasticizers with specially designed molecular architectures (molecular weight, side chain length, anionicity) was successfully synthesized. All synthesized PCEs exhibited high macromonomer conversion rates as well as relatively low PDIs indicating high quality. Dispersing efficiency of the synthesized IPEG PCEs was captured via spread flow and shear-dependent rheology tests in AAS or OPC pastes. It was found that in AAS pastes all polymers perform as highly effective superplasticizers and require extremely low dosages (similar to 0.05%). Whereas, none of the PCE polymers prepared could provide fluidity in OPC, even at high dosages (e.g. 0.3%). For a mechanistic understanding, the interaction between the polycarboxylate superplasticizers and AAS and OPC was investigated via adsorption and zeta potential measurements. It was concluded that all IPEG PCE samples produced typical Langmuir adsorption curves on AAS pastes, but exhibited linear relationships in cement pastes which signifies precipitation of these PCEs from the pore solution. The study highlights the disparity in performance of specific superplasticizers in different binder systems resulting from their different surface chemistry. Specific molecular motifs are required to address these differences in surface compositions at the atomistic level.