A filtered water supply is pumped through a high pressure hose at around 1,000 bar to a carefully designed nozzle. Water leaves the nozzle in a fine stream at a velocity faster than the speed of sound and is directed onto the surface of the concrete. Hydraulic forces within the concrete then cause the surface to crack off in layers.
Conjet technical director Carl Stromdahl claims to be the inventor of automated water jetting in the early 1980s while working for Atlas Copco. He believes that mechanised hydro-demolition will eventually revolutionise the repair of concrete structures and is developing new products to make the technique easier to use.
Conjet's latest model is controlled through an LCD display which can be programmed with the speed, depth and width of cut. The machine is versatile enough to follow curved surfaces, work in roof spaces of only 1.9m or reach up to 6m with full stability. And a new mini-tracked machine for use in sewers and small diameter tunnels is on the way.