Double-Beam Vibratory Screeds

A double-beam screed carries two parallel profiles and is pulled along guides or formwork edges, so it reproduces the set level across widths of up to 7.2 m. A floating screed uses a single 2–4 m profile steered free-hand, so flatness depends on the operator's skill. The twin-beam design also strikes off surplus mix and compacts concrete in one pass.

Pick a profile roughly 15–30 cm wider than the concreted strip on each side, so both ends stay seated on the guides. Floors poured between walls are usually handled with 1.5–4 m beams, while slabs in industrial buildings and road panels call for 5.2–7.2 m profiles. On the widest beams an underpowered drive loses amplitude towards the ends.

A 230 V unit suits work inside industrial buildings and car parks, where exhaust fumes are unacceptable. The 400 V version delivers more torque on long profiles and in continuous work, but needs an industrial three-phase supply. A petrol drive of the Honda GX class frees the crew from cables on roads and foundations without mains power, at the cost of weight and engine servicing.

Two operators are standard, one at each end of the beam, drawing it along the guides. Above roughly 5 m of working width a rope winch keeps the travel speed constant. Match travel speed to the mix: too fast leaves voids in the surface, too slow draws cement laitance to the top. Overlap consecutive runs by 10–20 cm.

A screed compacts mainly the near-surface zone, in practice down to about 15–20 cm of layer thickness — a drive of roughly 3 kN centrifugal force reaches no deeper. Raft foundations 25–40 cm thick and densely reinforced elements must be compacted first with a poker vibrator, usually 38–58 mm in diameter. Sequence: place the mix, compact it internally, screed it, then power trowel once bleed water has evaporated.

Twin-beam sets are modular: the drive unit, whether 230 V, 400 V or petrol, is sold separately from the working profile, and profiles run from about 1.5 m to 7.2 m. Adding a second beam of a different length to a drive you already own covers a new pour width. Check the mounting first — Altrad Belle and Enar systems are usually not interchangeable.