Shotcrete is a method of applying concrete onto surfaces at high speed. It is a mix of concrete or mortar, or even small-aggregate concrete. The common method of using what we also call ‘sprayed concrete’ is by applying a mix of dry materials and water in a continual feed through an open hopper and a rotary gun.
BLEND plants offer inventive, mobile plant solutions that can cater for both used versions of shotcrete – either wet-mix or dry-mix. Plants in the E-Series, suitable for smaller projects, provide electronic control to generate the desired mix and production of up to 70 m3/hour. In case of the larger projects where continual wet mix batching is required, one A-series plant can produce up to 120 m3/hour.
Applying shotcrete
Shotcrete is applied using a dry-mix or a wet-mix process. Both need pneumatic help to apply the required pressure at high speed to compact or clump the cement. When applying the product, operators use mechanised equipment that can achieve the required velocity at a consistent rate. One could do this manually, but the results are not up to standard for most requirements.
Both dry-mix and wet-mix methods are usually applied to a latticework or framework of rebar (steel mesh) or even a mixture of the two. This webbing helps the product to bind and, once it is in place, can be easily molded to achieve the desired shape.
Uses of shotcrete
- Swimming pools, tanks and artificial ponds
- Tunnel walls / Retention walls
- Mining applications (usually underground)
- Bridges
- Structural repairs to reinforcement
- Marine repairs
- Spillways (a passage for surplus water from a dam)
- Slope protection
Dry-mix shotcrete
The dry materials are delivered using air power to the nozzle through the hose from a hopper. At the nozzle the water is added to the mixture, resulting in both products delivered simultaneously to the surface. The operator controls the addition of water at the nozzle. Readers should note that the dry shotcrete is only fully mixed once the spray reaches the surface, as the individual materials travel alongside each other and only mix with the pressure and force delivered on impact. Dry-mix applications are useful when for repair work and when applying shotcrete to surfaces overhead, where the operator frequently stops for the workflow for readjustments or repositioning. This dry-mix shotcrete is also called gunite, even though the components of this type of concrete are essentially the same.
Wet-mix shotcrete
Most construction operators regard this method to be the easier of the two types of shotcrete, as they can pre-mix the final product at the hopper stage. The mix is delivered through the hose at a consistent rate and there is a compressed air line which then sprays the product to the surface area at high velocity. Wet shotcrete seems to be the ‘cleaner’ option of the two types, as there is no dust and operators have less waste falling to the ground (also called rebound). They can either apply wet-mix shotcrete manually with someone managing the hose or rotary gun or else, for larger projects, they can attach it to a crane or telescopic and control the process remotely.
Innovation is a fundamental feature of BLEND Plants Africa, paying attention to all aspects of the construction industry. Their professional teams recognise customer challenges and needs, leading to the development of solutions that will beneficially impact such activities. BLEND Africa’s goal is to offer equipment that will improve the quality, the efficiency and, particularly, the profitability of all their customers’ projects. Contact Blend Plants for more information on your specific needs.