Ultrasonic wave tests were applied on the large size specimen made of self-compacting concrete and rock filled concrete since the early age. Based on the viscoelastic medium wave theory， the viscosity parameter was separated from P-wave velocity test data and used for the assessment of work ability of the fresh rock filled concrete and hardened state of the rock filled concrete. It can be concluded that due to the complexity of the inner structure of rock filled concrete， the average P-wave velocity and the coefficient of variation of the representative element volume can hardly be used for the construction quality assessment； the high density layered detection has to be applied. Comparatively， much less detection will be enough based on the viscosity parameters separated from the P-wave data. The test of early age ultrasonic wave would be helpful to overcome the difficulties brought by the excessive size of the representative element volume in rock filled concrete.