Response of UHPFRCs in Tension under High Stress Rate

The paper presents a part of a full-experimental campaign characterizing various Ductal® mix designs (compressive strength of 150, 170, 210MPa) with various dosages of fibers (2% and 3.25%). The dynamic tests are performed by means of two Modified Hopkinson Bar devices with that are installed at the DynaMat Laboratory in Lugano. The tests, in tension at different velocities were performed on cylindrical notched specimens of 60mm in diameter and 60mm height (notch/radius = 0.20). The preliminary results present different rate sensitivity of the materials. Different behaviours are registered for the materials having matrix with special thermal curing respect to those cured as usual. An important increment of stress was obtained for the matrix where sand was partially replaced by Silica Fume. These results are the base for better understanding the mechanical behaviour in dynamic that will be obtained by further tests on Ultra-High Performance Fibre-Reinforced Concretes (various Ductal® classes). Such data will provide designers better overview of relevant properties of these materials for design of protective structures