The interaction mechanism of polycarboxylate and β-naphthalene sulfonate superplasticizers: Synergistic adsorption rather than competitive adsorption

Abstract

The challenge of compatibility between polycarboxylate superplasticizer (PCE) and β-naphthalene sulfonate superplasticizer (BNS) remains an enduring puzzle, requiring a comprehensive understanding of their interaction mechanism. In our study, the macroscopic properties, microscopic interfacial adsorption, and intermolecular forces are investigated in detail to elucidate the interaction between PCE and BNS. The results show that the dispersing ability of PCE and BNS decreases under different blending sequences. The increased adsorption of the blended superplasticizers indicates that PCE and BNS undergo synergistic adsorption on the surface of cement particles rather than competitive adsorption. Atomic force microscopy reveals a shift in the intermolecular forces of the blended superplasticizers from repulsion to attraction, including CH-π interactions and hydrophobic interactions. BNS adsorption on the PCE side chain results in the bending and collapse of the latter, which prevents PCE from providing steric hindrance. Moreover, PCE side chains wrap around BNS molecules, reducing the absolute value of zeta potential of cement particles' surfaces. The study, conducted through both experimental and theoretical methods, provides evidence that attractive forces between PCE and BNS have a disruptive influence on the original molecular structure.