Probing the effect of superplasticizer adsorption on the surface forces using the colloidal probe AFM technique

The interactions between adsorbed superplasticizer layers have been studied using direct force measurements, with an atomic force microscope. MgO was used as a nonreactive model system for cement, and a novel freeze granulation method for the production of spherical particles suitable for the colloidal probe atomic force microscope (AFM)-technique is reported. We found that the interactions induced by the adsorption of the anionic acrylic ester-ethylene oxide (AAE-EO) copolymers can be described as electrosteric, with an electrostatic and steric contribution. The range of the steric repulsion varied between 1.5 and 5 nm and could be related to the length of the grafted ethylene oxide chains. The lignosulfonate also induced a significant steric contribution that could be related to a dense coil conformation of the adsorbed superplasticizer.