Minimize Rebounding in Shotcrete Machine

Shotcrete machine is a wet mix technique that produces a high velocity cone-shaped spray pattern via pneumatic mechanism onto a horizontal or vertical surface. Increase the air from the shotcrete nozzle to increase the velocity and the compaction of the particles and produce a denser concrete. Shotcrete machine uses either aggregates or mortar. When you need to apply concrete vertically but do not want to deal with formwork and poured in concrete. Concrete gunite machine works best for covering or repairing curved surfaces like swimming pools, bridges, tunnels, dams, slope reinforcement… Shotcrete uses a wet mix so the water/concrete ratio is very important and controlled by the nozzle man. It needs to be low (under 0.5) to obtain a denser and water-resistant mix. This will also help reduce shrinkage and lower permeability in the finished product. One of the problems with shotcrete is the loss of material from concrete ricochets off the target surface due to the high velocity of the spray. This causes having to use more concrete, longer application times etc. The result can be vastly different when it comes to the properties of the in-placed concrete mix. If you use steel fibers as a distribution solution, the problem is even more problematic than with aggregates. According to Austin and Robins (1995), aggregates rebound is about 20-30% whereas with steel fibers, rebounding can reach 35-78% (Morgan et al., 1987; Banthia et al., 1992) with dry-mix shotcrete. With such high rebound, compaction is reduced and the concrete strength ends up greatly compromised. The rebound of non-adhering material during a gunite operation (using a dry process) is greater than during a shotcrete job (wet process) because gunite requires a much larger air compressor. On a gunite job, the rebound material can be reused, whereas, on a shotcrete job, the non-adhering material is wasted. Removing it is time consuming, slows progress and can be costly. So choosing the right technique for the job is essential.