In the context of the present master thesis a pure cement mortar with a compression strength higher than 10^8 N/m² (100 MPa) and permeabilities higher than 10^(-15) m² (1mD) should be produced. These target values should be reached by variation of w/c-ratio, plasticizer addition and initiation of a micro crack network, which could be realized by addition of magnesia sinter or sand in combination with adequate sample conditioning. A literature research has been done to find out the most suitable method for defining the permeability of pure cement mortars. A stationary permeability measurement method based on CEMBUREAU-procedure was chosen and the measurements were done with the help of a gas permeameter of the company VINCI-Technologies. The measurements of permeability delivered values with a high statistical dispersion. Tests done to analyze the reproducibility of the measuring method pointed out that a standard variance of ± 20% should be expected for measurements done on the same cement mortar sample. The permeability values of different compositions of pure cement mortars were located in a measuring range between 0,1 and 2,7 mD. The closest result to the target value was achieved by samples with a w/c-value of 0,35. The compression strength in this case was equal to 75MPa and a permeability varied between 0,4 and 1,1 mD. According to the measurement data no significant dependence between the permeability and different w/c values or addition of plasticizer has been observed. On the contrary, the compression strength of the samples was strongly connected to their w/c value: decrease of w/c-value lead to higher the compression strength values. The initiation of micro cracks did not lead to increase of the permeability as it was expected.