Slurry infiltration is important in various building processes in civil engineering, especially in tunnel construction, diaphragm walls and well borings. To enhance comprehension of slurry infiltration in these constructions, or similar projects, various factors influencing slurry infiltration characteristics were experimentally investigated, including: types of bentonites and sands, seawater, degree of saturation of the sand, hydraulic gradient, and pressure applied. Results of this research are used to lower the permeability of the bottom of a canal in the Netherlands (Twente Kanaal). Additionally, the airtightness of the filter cake was also studied, since this is an important safety aspect.