Vibratory Truss Screeds cause concrete to flow in all directions. Excessive buildup ahead of a vibratory screed causes concrete to slip through, elevating the final grade. Vibrating screeds bring the grade to an average, rather than actually cutting away the high material. As with manual screeding, placement requires workmen to fine grade ahead of the screed. Vibratory Floating Screeds are guilty of porpising because they lack reference for elevation. They continually adjust between too high and too low.

Laser Screeds are the ultimate vibratory screed because they cut away excess placement with an auger ahead of the vibratory beam. These machines do not require screed rails as they read a laser beam for elevation. They lack the versatility to place in tight places and overhead decks but they perform well in slabs of open acreage. For the builder with the funding and technical support for this machine, it makes great sense.

Slipform Pavers are incomparable in their scope of performance. The builder who faces the demands of placing high performance mix designs in long parallel runs has no other option. The funding and technical support for this machine is part of the territory.

The Friction Screed. Some are self-propelled as triple tubes. Some are self-propelled and carried by a structure which travels over the slab such as a bridge deck paver and a channel paver. Like other pavers, these are heavy machines, requiring substantial logistics to transport and set up for operation. The Bunyan Striker is a light tool, easily transported, with powerful control of surface grade. This uses the same tool for both placement and screeding. It is used to aid delivery, cut away excess placement, then screed. Unlike vibratory screeds, the friction screed leaves aggregate matrix of the concrete intact. The performance of concrete is most recognized in the material at the surface. This is where aggregate provides critical durability for the life of the slab.