Abstract: Time-dependent fracture behaviors in mass concrete closely relate to the safety of concrete structures in service. To investigate these behaviors of concrete under sustained loads, this study conducts wedge-splitting tests under a long-term constant load at 85% of the maximum load, using compact tension specimens in three different sizes. The test results indicate three development stages occur in timedependent crack mouth and crack tip opening displacements and time variations in crack mouth opening rate: deceleration, stable development, and accelerated failure. Compared with the static fracture test on the same specimen size, a larger critical crack mouth opening displacement occurs in the present longterm constant load test. And a highly linear correlation can be observed between the displacements at the crack mouth and the tip. In addition, the geometry relation between the opening displacement and propagation length of cracks fits in well with the hinge model.