Vibratory Screeds for Precast Concrete. A Concrete Vibrating Screed that uses dual, counter-rotating, 115 VAC, synchronized vibratory motors uniquely mounted to 6"W x 4"H x 6'L to 18'L aluminum beam to self-propel the Screed down the form as it quietly spreads, consolidates, levels, and surface finishes conventional, high-flow and self-compacting …