True Triaxial Testing device (TTT)

The TTT facilitates the characterization of the behavior of bound road construction materials (e.g., asphalt, concrete) under triaxial loads with load parameters relevant to roads, such as traffic, temperature, and relevant load frequencies. The generation of loads up to 63.5 kN with loading frequencies of up to 10 Hz is achieved on cube-shaped test specimens using hydraulic cylinders under sinusoidal tension-swell, compression-swell, and tension-compression alternating loads. This is performed within a temperature range of -20 to +70°C. The rheological phase-shifted response of the material to the load pulses allows the load maxima in the respective load directions to occur with a time delay. The resulting elastic and plastic deformations are measured synchronously in all directions with an accuracy of 1 µm. The TTT facilitates the unprecedented characterization of the material behavior of road construction materials under realistic loading conditions. The findings provide a foundation for developing models that simulate the behavior of these materials and, consequently, for the structural modeling of road pavements in collaboration with various sub-projects of the SFB/TRR 339 "Digital Twin Road." The aim is to develop a suitable method for predicting the service life of road pavements in order to optimize the construction materials and structure of road pavements according to sustainability criteria.