Abstract: The influence of age on Double-K fracture parameters of roller-compacted concrete (RCC) was investigated via fracture test on eighteen RCC wedge splitting specimens at different ages (28 d, 60 d, and 90 d). The effective crack length, initial fracture toughness and unstable fracture toughness of the RCC specimens of different ages were acquired. Results revealed that with the growth of age, the critical pressure for initial cracking and critical pressure for instability both expanded, and the ratio of critical pressure for initial cracking to critical pressure for instability also increased. With the age increasing from 28 d to 90 d, initial cracking toughness Kⁱⁿⁱ_IC and unstable cracking toughness K^un_IC climbed by 0.216 0 MPa·m^1/2 and 0.292 2 MPa·m^1/2, respectively; the ratio of Kⁱⁿⁱ_IC to K^un_IC maintained between 0.5 and 0.6 in general. Effective critical cracking length and subcritical crack extension both changed in a negative relation with age, implying that smaller age results in better toughness of specimens.

Key words: roller-compacted concrete, double-K fracture parameters, age, wedge splitting test, fracture toughness