Recommendation for concrete mix design to prevent bleed channels on diaphragm walls

Abstract

Diaphragm walls are used either to support excavation walls on site or prevent water move through the ground. The observations recorded following excavation and planning of diaphragm walls demonstrate that concrete outside the reinforcement cage is of a poorer quality than the one inside the cage. These disorders are mainly chimneys of water upwelling. To prevent their appearance on project sites, the concrete used for the realisation of diaphragm walls must meet the requirement of EN-1538 and EN-206/CN. Despite of this requirement, some diaphragm walls present disorders. This study stands on conducted on site and completed in the laboratory. Test results showed that the bleed water yield value of 24.4 ml, conducted using a press filter (Bauer) prescribed in the recommendations is too high. A limit of 15 ml of the relative volume of water is porposed with the press filter conducted during 5 min at 5-bar.