Toughness and characterization of reactive powder concrete with ultra-high strength

A number of three-point bending and fracture tests of 200 MPa-level reactive powder concrete (RPC) with the various fiber contents have been conducted to probe the nature and characteristics of toughness of RPC200. The contribution of the embedded fibers to improving the crack-resistant capacity, energy absorption capacity and toughness with various deformation mechanisms has been analyzed. Taking account of that the first-crack deformation, peak-load deformation and their improvement varied with the fiber contents and that the deformation mechanism affected differently the performance at the first crack and the peak load, we took the peak-load deformation of plain RPC200 as the reference deformation to measure the toughness of fibered RPC200. Two toughness indices T _2(n−1)(n) and FT _2(n−1)(n) have been formulated based on P-δ responses and P-CMOD responses. The indices quantify the toughness of RPC200 with the various deformation mechanisms relative to perfectly elastoplastic materials by setting the toughness level 2(n−1) as the initial reference. It is shown that the toughness index T _2(n−1)(n) reflects the function of fibers to improve the toughness of RPC with the deformation throughout specimens, but overestimates the contribution to enhancing the toughness in post-peak periods. It underestimates, on other hands, the contribution to improving the toughness in the period from the first crack to the peak load. In contrast, the toughness index FT _2(n−1)(n) properly presents the capability that fibers absorb energy and constrain crack propagation in the matrix when the deformation is concentrated on the open crack. The proposed index unveils the contribution of fibers to toughening RPC200 both in the period from the first-crack to the peak load and in the period of post peak. This characterization method not only reveals the nature of toughness but also levels the toughness of RPC200. It could provide a way to establish an objective toughness characterization for RPC200 and facilitate its applications. Supported by the New Century Excellent Talents Program (Grant No. NCET-05-0215), the Natural Science and Engineering Research Council of Canada (Grant No. PGS D2 2006), the Laboratory Innovation Plan of Beijing Science and Education Committee (Grant No. JD102900671) and the National Basic Research Project of China (“973” Project) (Grant No. 2002CB412705)