Do superplasticizers work the way we think? New insights from their effect on the percolation threshold of limestone pastes

Superplasticizers are polymeric dispersants that play a major role in concrete technology. Despite their ubiquity and much research on their working mechanisms, many questions remain about the effects of their molecular structures on their working mechanism, in particular their ability to lower the yield stress of particulate suspensions. It is generally recognized that superplasticizers decrease attractive interparticle forces, thereby reducing or eliminating yield stress. It is also often assumed that changes in yield stress should be proportional to changes in interparticle forces. This paper takes a fresh look at this question, revisiting Yodel (YD) and modified shifting factor (MSF) models that not only incorporate interparticle forces, but also percolation thresholds. This leads us to conclude that a major impact of superplasticizers is to modify the percolation threshold in direct relation to their adsorption.