Kneading and extrusion of dense polymer–cement pastes

The kneading and extrusion behavior of dense polymer-containing cement pastes has been investigated. Both the polymer to cement ratio (p/c) and the water to cement ratio (w/c) were varied. Three types of polymers – one adsorbing and two non-adsorbing on cement – were used. The kneading and extrusion parameters (dispersion energy, torque plateau value, extrusion pressure, paste ageing) were determined using instrumented kneader and ram extruder. As will be shown, the most important parameters controlling the efficiency of the kneading and extrusion processes are the cement volume fraction on the one hand and the polymer concentration in the interstitial solution on the other hand. Polymer adsorption is not a key phenomenon, whereas hydrodynamic lubrication is important. A simple free volume model for paste extrusion is proposed.