Effects of cations on the yield stress of a highly concentrated suspension of glass beads with the addition of polycarboxylate superplasticizer

Abstract

The effects of potassium and calcium ions on the yield stress of highly concentrated suspensions of glass beads in the presence of polycarboxylate superplasticizer (PCE) was investigated in this study. It was found that the presence of ions, regardless of whether they are calcium or potassium, can significantly increase the yield stress of glass bead suspensions (GBS) without polymer. Moreover, the increase is proportional to the ion concentration and has no relevance to the isoelectric point of GBS. For the GBS with only addition of PCE, increasing the PCE dosage firstly decreased yield stress and then led to its increase. For the GBS in the presence of both ions and PCE, increasing [K+] led to higher yield stress, while increasing [Ca2+] firstly increased yield stress and then decreased it. The results indicate an interaction of ions with polymer exist which determines the rheological properties of GBS. Firstly, increasing [Ca2+] is beneficial for PCE adsorption on the surfaces of glass beads (GBs), but increasing [K+] has the opposite effect. Besides, it is hypothesized that, the incorporation of calcium ions changes the adsorption structure of PCE on the surface of GBs.