Prediction of Concrete Pumping: Part I—Development of New Tribometer for Analysis of Lubricating Layer

The character of the lubricating layer formed near the wall of a pipe during the flow of pumped concrete is a dominant factor facilitating concrete pumping. To predict flow rates of concrete transported by pumping, it is necessary to measure the rheological properties of the lubricating layer before pumping. In this article, a new version of a test instrument called a tribometer is developed, by considering the level of shear rate that induces the lubricating layer during real pumping. A test method is also suggested based on numerical simulation of the shear flow inside the tribometer and, finally, equations capable of transforming the values measured in the new tribometer into the rheological properties of the lubricating layer are derived. Work in this article will be extended in a subsequent study, in which, full-scale pumping tests will be performed, and predictions for concrete pumping based on the measurements of the new tribometer will be verified from comparisons with the test results.