This thesis examines the strength and stiffness of shotcrete used in tunnelling. Short- and long-term uniaxial compressive strength (UCS) tests were conducted. Short-term tests were used to determine the evolution of strength and Young's modulus, whereas long-term testing with a predefined deformation rate was used to analyse the evolution of the stress-strain-behaviour of the wet shotcrete. Petrographic examinations of the concrete aggregates were performed and brought into relation to the properties of the shotcrete. Four series of shotcrete samples were taken during the construction of the Semmering Base Tunnel (construction lots SBT 3.1 Grautschenhof and SBT 2.1 Fröschnitzgraben). Deformation controlled short-term tests were done at shotcrete ages of 1, 2, 3, 5 and 10 days. Additional uniaxial compressive strength tests were conducted with a constant stress-rate on samples older than 30 days. The rate of deformation for the long-term tests was set to 0,6 % for the first 24 h, 0,2 % up to 48 h and 0,1 % until the end of the test. Results of the short-term tests show high uniaxial strength. The mean values of strain obtained from the long-term tests at the maximum stress level are between 1,02 % and 1,47 %. Concrete aggregates were analysed using petrographic microscopes. Cuts from the concrete cores used for the UCS tests were examined with scanning electron microscopy (SEM). A correlation between the petrographic properties of the aggregates and the stress-strain-behaviour of the shotcrete couldn't be observed within the scope of this thesis.