EXPERIMENTAL MEASUREMENT AND EVALUATION INDEXES OF TOUGHNESS PROPERTIES FOR UHTCC UNDER UNIAXIAL COMPRESSION

Toughness index is one of the important mechanical indexes to evaluate the unique mechanical performance of Ultra High Toughness Cementitious Composites (UHTCC). Comparing different testing and evaluating standards of flexural toughness for steel fiber reinforced concrete used in various countries, the fiber reinforced concrete standards of America (ASTM C1018), Deutschland (DBV), and Austria (ORSp) are referred. Five toughness indexes are used from different points of view to quantitatively evaluate the compressive toughness of UHTCC in detail. These indexes include the equivalent compressive strength feq,n , the post-crack deformation energy , the toughness class, the relative toughness index RT1 for evaluating fiber effect, and the relative toughness index RT2 for evaluating the post-peak toughness of UHTCC. The test results, which are obtained from six groups of UHTCC at different compressive strength between 33MPa and 52MPa, indicate that the deformation energy after cracking and the equivalent compressive strength increase with the compressive strength. The relative toughness indexes of RT1 and RT2 show that the toughness of UHTCC is 2.6―3.8 times of the matrix, and the post-peak toughness of UHTCC is 1.7―2.2 times of pre-peak toughness. The fiber effect mainly improves the post-crack toughness. The toughness classes of UHTCC are mainly between class 1 and class 2. All of the indexes demonstrate that UHTCC possess high compressive toughness and plastic deformation capacity, and high post-crack load bearing capacity.