Interactions between Non-Ionic Additives and Cement Phases

Abstract

For a variety of applications the use of polymer modified cement mortar (PCM) or polymer modified cement concrete (PCC) is state of the art. It is a matter of common knowledge that interparticular interactions between the mineral and polymer components, more precisely the adsorption behaviour and film formation processes of polymer particles, cause a change of properties in comparison to a concrete without any modification. The affinity of polymer particles to mineral surfaces determines the adsorption behaviour significantly and thus the microstructure formation of the entire system, in which mineral and polymer phases penetrate one another. A quantitative prediction of cementitious surface preferred by non-ionic stabilized polymer particles to adsorb, was aspirated by titration experiments carried out with electroacoustic zeta potential measurements and turbidity measurements of polymer modified pastes carried out by spectrophotometry. Measuring the change of zeta potential of several cementitious components by a stepwise addition of polymer dispersions, do not require a variation of variables of the system. It can be measured without any treatment of the powdery raw materials or dissolution of the considered suspension. Equally the polymer dispersions were used in their original state. Spectrophotometric analyses were used to determine the concentration of polymer particles in the liquid phase of fresh polymer modified cement-paste or pastes of additives like quartz powder. The preparation of dilution series allowed the assessment of desorption behaviour as well as the prediction of the amount of adsorbed particles. Finally affinities of non-ionic stabilized polymer particles to several mineral surfaces in a state constituted, fresh paste could be described as a result of chemical induced repulsive or attractive forces and physical repressions, like the absence of sufficient space in liquid media for dispersed polymer particles. The central role of non-ionic stabilizers in adsorption processes was exposed especially by electroacoustic zeta potential measurements.