Vibrator trails are streaks of high-paste-content, low-air-content concrete found in the vibrator paths of some slipformed pavements. They are caused by excessive vibration of concrete and are prone to longitudinal cracking. In 1995, a field research project was initiated in Iowa to evaluate the effect of slipform-paver vibrations on the air content of hardened concrete. The study, which involved three separate interstate paving projects, examined three variables: vibrator frequency, paver speed, and vibrator position within the concrete slab.
