Study of Vibration in Concrete,Report 3. Mechanics of Motion of Fresh Concrete.

摘要

Mechanical impedance tests on fresh concrete revealed the properties that resist motion. It was found that there were two distinct mechanical impedance curves depending on whether the dynamic stress applied was above or below a threshold level. At low stress levels, the impedance of the mixture was almost flat, possessing high damping, stiffness, and mass characteristics. No resonant frequency was found, but on the contrary, a wide spectrum of frequencies would produce sufficient motion for consolidation. It is likely that fresh concrete requires a continuous spectrum of energy over a wide frequency range to produce consolidation rather than discrete or optimum frequencies. Since concrete has a continuous spectrum of particle dimensions, it is probable that vibrators should supply energy over a spectrum of frequencies. Tests are planned to study the consolidation of concrete with impulses rather than a sinusoidal motion as impulses contain energy over a wide band of frequencies.