Instrumentation of Paver Vibrators, MLR-95-10, 1999

Premature deterioration of Portland Cement Concrete (PCC) pavements led to investigations for causes of the concrete failures. Evidence of parallel longitudinal cracks in deteriorating pavements, with crack spacings similar to paver vibrator spacings, made it clear that the vibrators were related to the cause for deterioration. After a number of field trips observing paving operations and measuring vibrator frequencies, it soon became clear that the paver vibrators were, in many cases, not running in compliance with the Iowa DOT specification. The specified frequency was from 5000 to 8000 revolutions per minute (rpm). The pavers visited did not have a monitoring system to give a continuous frequency readout for any of it's vibrators. Occasionally, during a paving operation, frequency readings were taken on some vibrators with a hand held tachometer. However, that degree of monitoring was found to be far from providing the quality of information and control necessary to maintain compliance to the Iowa DOT specification. A paver vibrator monitoring system, which would operate continuously while paving and cover all vibrators, was determined to be essential. The output must be visible to the paver operator and inspector at all times.