Dispersing Efficacy of Tailored IPEG PCEs in AAS Binders: Elucidating the Impact of PCE Molecular Weight

Abstract

In this study, the impact of the molecular weight of isoprenol ether-based (IPEG) polycarboxylate superplasticizers on the dispersing effectiveness in sodium hydroxide-activated slag binder and slag composite cement was investigated. For this purpose, a series of IPEG polycarboxylate ether (PCE) superplasticizers possessing the same anionicity and the same side chain length but varying molecular weights (13,000−400,000 Da) were prepared. The synthesized PCE polymers were then subjected to application-related tests. It was found that their dispersing capacity in the AAS binder differed significantly and that IPEG PCE polymers possessing higher molecular weight generally were more effective. Surprisingly, it was also noticed that in the slag composite cement (90% slag, 10% OPC), generally, higher doses of the PCEs were required than in the OPC-free AAS binder system. Moreover, the working mechanism behind the enhanced dispersing ability of high M w IPEG PCEs was studied via adsorption and adsorbed layer thickness (ALT) measurements. To determine the ALT of the adsorbed PCE polymers, phosphate-modified polystyrene nanoparticles were selected as a model substrate. Results from dynamic light scattering revealed that high M w PCEs produce thicker adsorbed layers, which highly benefits the dispersing power of the PCE polymers stemming from enhanced steric hindrance. Finally, different models for the adsorbed conformations of those IPEG PCEs are proposed based on their individual molecular characteristics.

Production of bio‐based concrete water reducers from renewable resources: a review

“…32 This is due to the presence of comb-like sidechain structures with functional groups in the molecule, which are adsorbed and act as barriers keeping the cements particles far apart from each other to ensure proper hydration and dispersion. [33][34][35] On the other hand, natural carbohydrate water reducers like cellulose, starch or their derivatives can disperse cement particles via the electrosteric effect because of their high molecular weights from repeating glucose units and the presence of charged -OH and carboxyl functional groups within their structures. 36 Studies have thus shown that the mechanism of dispersion of these bio-based water reducers have potential impact on the final properties of concrete such as the setting time.…”

“…Polycarboxylates are high-range water reducers produced by esterification and transesterification reactions of unsaturated macro monomers of carboxylic acid and polyethylene glycols. 33 They possess comb-like structure consisting of a main backbone and several side chains. Figure 8 illustrates the chemical structure of a typical polycarboxylate (PCE) superplasticizer.…”

“…For example, the synthetic polycarboxylate ether (PCE) water reducer known for its superplasticizing properties function largely by steric hinderance on cement particles when mixed in concrete 32 . This is due to the presence of comb‐like side‐chain structures with functional groups in the molecule, which are adsorbed and act as barriers keeping the cements particles far apart from each other to ensure proper hydration and dispersion 33–35 . On the other hand, natural carbohydrate water reducers like cellulose, starch or their derivatives can disperse cement particles via the electrosteric effect because of their high molecular weights from repeating glucose units and the presence of charged ‐OH and carboxyl functional groups within their structures 36 .…”

Reconfiguring Molecular Conformation from Comb-Type to Y-Type for Improving Dispersion Performance of Polycarboxylate Superplasticizers

“…The side chains of PCEs repel each other on the cement to form a comb conformation and extend to the solution, thus causing steric hindrance and dispersion among cement particles. 21 Some scholars have tried to modify PCEs by side chain hyperbranched. Li et al introduced a hyperbranched polyamide monomer into PCEs, improving the dispersion ability of PCEs and the early compressive strength of concrete.…”

Multidimensional Branched Composite Binder via Covalent Grafting for High-Performance Silicon-Based Anodes

“…This way of the small molecules grafting the polymer does not reduce the overall density of polar groups as does the introduction of large molecules or the formation of cross-linked structures. Moreover, due to the less steric hindrance and multiple polar groups of small molecules (CA), compared to the larger steric hindrance caused by introducing macromolecules, − the CA- g -PAA binder can make more use of PAA-owned polar groups and provide more active sites through covalent bonding with −OH on the surface of Si. The bonding strength is enhanced between Si and the CA- g -PAA binder, thereby mitigating the volume change of Si electrodes, which reduces the isolated active particles formed by shrinkage and maintains the integrity of the electrode.…”