Title:
Avoidance of Blockages in Concrete Pumping Process
Author(s):
Denis Kaplan, Francois de Larrard, and Thierry Sedran
Publication:
Materials Journal
Volume:
102
Issue:
3
Appears on pages(s):
183-191
Keywords:
bleeding; blockage; process; pumped concrete; test
DOI:
10.14359/14446
Date:
5/1/2005
Abstract:
This paper describes a joint research project about concrete pumping. After a careful literature review was carried out, an experimental 148 m-closed-loop pumping circuit was built near Roissy, France. Over 68 concrete loads were pumped—a number of which were subject to blockage. These experiments led to significant advances in the understanding of the blockage process. Four types of blockages were pointed out. The most frequent happens at priming. It is due to coarse aggregate particles, which tend to leave the concrete front and to flow through the grout section, eventually forming a dense plug ahead of the flow. The tendency to segregate is correlated with bleeding, a phenomenon that is easier to reproduce in a small-scale test. Such a bleeding test was developed by modifying a conventional air meter, providing a simple and cheap site test. The initial bleeding rate was correlated with the likelihood of blockage in the pumping circuit. Finally, a broad analysis of the blockage formation could be proposed, giving clues to practitioners for a better control of the concrete pumping process.