Production of drainage concrete piles as draining elements of retaining walls

Phase 1: 2013
Phase 2: 2015 - 2016

The aim of this research project funded by the Federal Waterways Engineering and Research Institute (BAW), the Chair of Building Materials Technology together with the Department of Geotechnical Engineering of the of the University of Wuppertal, is to find a suitable approach from the point of view of geotechnical, construction process engineering and building materials aspects, in order to determine the and limits of a reliable production of drainage concrete bored piles as draining elements of shoring walls. The production of individual drilled piles of drainable concrete within overlapping drilled pile walls can be suitable in individual cases to prevent the build-up of water pressure behind the wall and thus make the entire shoring construction more economical. The aim of the laboratory tests is to prepare suitable concrete compositions for initial testing in situ. Selected material compositions will be investigated and analyzed with regard to their properties in the laboratory and testing facilities of the Ruhr University Bochum. The aim is to optimize the compositions with regard to adequate processing and the necessary properties such as compressive strength or water permeability.
In addition to the determination of classical properties, the determination of the erosion resistance of the cement paste is of particular importance. It is particularly important if the fresh concrete comes into contact with water (e.g. groundwater) during placement. Drainage concrete - in contrast to normal concretes, which have a sufficiently compact microstructure and good cohesion in the fresh state - can be completely flushed through by water due to its piling spores. There is an increased risk of washing out of the cement paste. In order to minimize this, a pronounced adhesion behavior of the binder glue is to be aimed for, so that even after flowing through, adhesive glue remains on the coarse aggregates and can bring about the required firm bond between them. It is to be investigated to what extent it is possible to counteract this behavior by adding additives that are considered appropriate, such as plastic dispersions, stabilizers or UW compounds specially developed for underwater concretes. At the same time, the focus is on the installation of the concrete in practice. The properties required for classic placement methods (e.g. contractor methods) are taken into account. In addition, alternative installation methods are also investigated and the associated requirements for the fresh concrete are included. For example, a method is conceivable for the placement of drainage concrete in which it is placed via a continuously drawn pouring pipe. This placement method is suitable for concrete with a stiff consistency and consequently insufficient flow behavior for the contractor method. With this method, the drainage concrete emerges from the discharge pipe under its own weight alone.