A study on cement-poor concrete with talc for borehole sealing in rock hosting radioactive waste

The paper describes the performance of a concrete intended for sealing deep boreholes in the host rock of radioactive repositories. The concrete will form plugs where fracture zones are intersected and be located between very tight seals of smectite clay installed where the surrounding rock is tight. The concrete must be able to carry the clay segments after a couple of days but the bearing capacity does not have to be very high since the clay soon adheres to the rock and carries itself. The concrete contains talc as superplasticizer since ordinary organic additives for reaching high fluidity at casting are unwanted. It has a low cement content for maintaining its low porosity after dissolution in a long time perspective.