Abstract
The interaction of different charged polymers, namely anionic polycarboxylate superplasticizer (PCE) and neutral polyethylene glycol (PEG) with potassium ions, and their effect on the yield stress of highly concentrated glass bead suspension (GBS), were studied under different concentrations of potassium ions ([K+]). It was found that, compared to the neutral PEG, the negatively charged PCE can be adsorbed on glass beads (GB), and then decreases the yield stress of GBS. The increasing concentration of free polymer in the interstitial liquid phase with the increased polymer dosage leads to the higher yield stress of GBS, which may be caused by the higher depletion force. In addition, this effect is also related to the charge density of the polymer and the [K+] in the solution. Along with the increase in [K+], the yield stress of GBS increases significantly with the addition of PCE, but this cannot be observed with PEG, which indicates that potassium ions can interact with negatively charged PCE instead of the neutral PEG. At last, the interparticle forces between two single GB with adsorbed PCE in solutions containing [K+] and PCE were measured by colloidal probe atomic force microscopy to better understand the interaction of the charged polymer with counterions.
Highlights
IntroductionFor concrete with a low w/c ratio, such as self-compacting concrete (SCC) or ultra-high performance concrete (UHPC), a high dosage of Polycarboxylate superplasticizer (PCE) is needed to achieve the desired flowability
glass bead suspension (GBS) in the presence of Polycarboxylate superplasticizer (PCE) were studied [18], and in this paper, we mainly focus on the interaction of different charged polymers with cations and their corresponding effect on the yield stress of GBS
In contrast to the first decrease and increase in the yield stress of GBS with the increasing addition amount of PCE [18], a monotonous increase of yield stress can be observed with the increasing dosage of polyethylene glycol (PEG), which is assumed to be caused by the depletion force, due to the non-adsorbing property of PEG on the surface of glass beads (GB)
Summary
For concrete with a low w/c ratio, such as self-compacting concrete (SCC) or ultra-high performance concrete (UHPC), a high dosage of PCE is needed to achieve the desired flowability. A large amount of PCE can result in a high concentration of non-adsorbed PCE which are left in the interstitial liquid phase [2,3]. PCE on the initial rheological performance of cement paste, which has been well explained by the combination of DLVO theory More and more researchers have gradually found that, in addition to the effect of the adsorbed polymers, the free polymers left in the liquid phase affect the initial
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