Effect of Electromagnetic Pulsation on the Rheological Properties of Mortars During Pumping

The basic understanding of the underlying mechanisms and the coherences between material properties and processing parameters, which are prerequisite for a better understanding and prediction of pumpability of concrete, mortar or suspensions, is an objective of numerous research activities. Current investigations aim to actively control the pumping process, hence being able to prevent blockages. Although much progress has been made in this research field recently, generally applicable models for the prediction of pumpability under consideration of the rheological properties of the material to be pumped as well as the process parameters are not available. Experimentally determined properties of the bulk material investigated in a small scale pumping test will be presented. We evaluated the effect of an externally applied alternating electromagnetic field with varying frequencies on the pumpability of the mortars regarding changes in pressure in the pipe as well as viscosity and yield stress of the bulk material. For the tests, two mortars with a constant solid volume fraction based on limestone powder (non-reactive) or ordinary portland cement (reactive) as solid phase have been investigated. Moreover, the lubrication layer formed at the interface between pipe and material during pumping, being the main influencing factor on pumping of cementitious materials, will be examined. The effect of the alternating electromagnetic field on the lubrication layer was experimentally simulated with a sliding pipe rheometer. Results for the bulk material and the lubrication layer will be compared. Moreover, the practical applicability of electromagnetic pulsation on the pumpability will be discussed.