Shotcrete
Shotcrete turns up in 2 fields: refractories, concrete. Here is what it means to the people in each one.
Shotcrete in refractories
Wet-mix gunning: castable pumped through a hose and set instantly by accelerator added at the nozzle.
A placement method in which a mixed low-cement castable is pumped like concrete to the nozzle, where compressed air and a set accelerator are added so it sticks and stiffens on impact. Compared with dry gunning, shotcrete gives higher density, lower rebound and less dust, close to cast properties. It is used for large linings such as blast furnace stack relines, cement preheater cyclones and big ducts.
"Stack reline is all shotcrete, two pumps running round the clock until the top is done."
Shotcrete in concrete
Concrete shot from a nozzle by compressed air and built up in layers on walls, slopes, pools and tunnels.
The nozzleman builds the section up in passes on slopes, tunnel linings, pools, retaining walls and repairs, often against a single-sided form. In the wet-mix process ready-mixed concrete is pumped to the nozzle and air is added there; in the dry-mix process, also called gunite, dry material is blown through the hose and the nozzleman adds water at the tip. Material that bounces off, called rebound, is waste and must never be worked back into the wall.
"Shotcrete crew's on the pool tomorrow, so have the steel inspected and the rebound from the last shoot cleaned off the deck tonight."