Prediction of concrete pumping performance based on the evaluation of lubrication layer properties

Abstract

In this dissertation, to propose prediction methods for the concrete pumping performance in the pipe, the properties of lubrication layer which is a dominant role in concrete pumping were evaluated. In order to predict the concrete pumping performance, the concrete flow typology within a pumping pipe should be carefully analyzed. When concrete is being transported in the pipe, the lubrication layer which forms in the vicinity between the concrete and pipe wall plays a critical role to facilitate the concrete pumping. Therefore, the mechanism for this layer formation is basically investigated with shear induced particle migration and investigated the particle concentration properties along the pipe diameter to quantitatively estimate the properties of lubrication layer. The change of particle concentration can result in different rheological properties in the concrete mixtures and it might influence the concrete flow conditions in the pipe. To demonstrate the effect of particle concentration distribution, various suspension models are used to simulate the concrete pumping condition. The concrete constituents, especially sand and gravel, have angular and irregular shapes that can cause different flow conditions. To consider the particle shape effects on numerical simulation, the intrinsic viscosity concept which measures the effect of individual particles shape on viscosity is used to simulate precisely the shear induced particle migration. To determine an optimum intrinsic viscosity considering the particle shape effects, the circularity concept which is one method to represent shape effects is quantified using digital image processing technique. These factors, i.e. rheological properties due to particle concentration changes and particle shape effects, are considered carefully when performing numerical simulations in order to precisely verify the concrete flow in pipe. Along with numerical approach, to estimate analytically the pumping pressure and flow rates...