The competitive adsorption characteristics of welan gum and superplasticizer in cement mortar

Abstract

Welan gum has been widely used in oil cement and grouting materials for its excellent rheological properties and anti-bleeding, and most of all, being friendly to the environment. However, when welan gum was added, the fluidity of mortar decreased sharply, so it should be used together with a superplasticizer to enable good workability. With its powerful charge density in the molecular structure, the competitive adsorption between welan gum and other admixtures happened remarkably during the addition process. Consequently, we experimentally studied on the bleeding rate and rheological properties of cement slurry, fluidity and mechanical properties of mortar with welan gum mixed with superplasticizer, aiming at understanding the competitive adsorption phenomenon by application of welan gum mixed with superplasticizer. By measuring the hydration heat and zeta potential, the mechanism of interaction of welan gum with superplasticizer was deduced and explained. The results showed that it could ensure a good dispersion effect when welan gum is mixed with the two kinds of superplasticizer. Welan gum had little impact on the naphthalene superplasticizer, but did have a substantial influence on polycarboxylate. In practice, adding welan gum after PCE acted with cement for 2 min could effectively avoid the competitive adsorption and then achieve better performance. On this viewpoint for mortar with PCE, new delay release welan gum needs further research and development.