Shotcrete: the difference between the dry and wet methods

This has an important consequence: the reach. Aliva states a conveying distance of 300 metres for dry mix, with pipes, and 40 metres for wet mix on the same machines. Beyond 80 metres, Aliva recommends steel pipes.

Dry-mix spraying

Long reach, so the machine can be positioned a long way off. The manufacturer states that the rotor machines Aliva-257 and -267 work well on sites with many interruptions. Aliva-201 for pressure silos is specified for long conveying distances and takes 16 mm aggregate.

Wet-mix spraying

Shorter reach, and the water is already in the mix when it leaves the machine. Aliva-257 and -264 are rated at 40 m / 15 m for wet mix, compared with 300 m / 100 m for dry mix.

The machines in the catalogue

The rotor machines cover 0.2 to 21 m³/h. Capacity depends on the rotor size, not on the model alone:

• Aliva-237 — 0.2–4 m³/h, 450 kg, dry-mix concrete. 4 mm aggregate with S rotor
• Aliva-257 — 0.7–9.6 m³/h, 650 kg, dry and wet mix. M rotor 1.9–5.0 m³/h, L 2.7–7.2, XL 3.6–9.6
• Aliva-264 — 7.1 or 10.7 m³/h (two speeds at 50 Hz), 1 465 kg, dry, earth-moist and wet mix
• Aliva-267 — 4–21 m³/h depending on version, 1 500 kg. Top Plus gives an infinitely variable 8.0–21.0 m³/h with a 26.5 l rotor
• Aliva-272 — spraying pump, 3–20 m³/h, 80 bar, 2 200 kg. 37 kW electric or 34.5 kW Deutz diesel
• Aliva-101 — spraying head for excavators, 210–230 kg, hydraulics 210–350 bar, radio remote control

Aggregate size in practice

Aliva-267 can handle 20 mm, but Aliva recommends a maximum of 8 mm. This is an important distinction: just because a machine can handle something does not mean it is designed for it.

The project decides, not the machine

Tunnels, rock support, pool construction and refractory linings make different demands. Describe the job — the distance from machine to nozzle, which concrete is specified, and how much needs to go on per hour — and we will tell you which way we would go.