Shotcrete
CSI Division 03, Concrete
Concrete or mortar pneumatically sprayed onto a surface at high velocity through a hose, placed either as a wet mix, pre-mixed with water, pumped, and sprayed, or a dry mix, dry materials sprayed with water added at the nozzle, used for pool shells, retaining walls, tunnel linings, and slope stabilization where conventional formwork isn't practical.
Why it matters
Shotcrete's quality depends heavily on the nozzleman's technique, holding the correct distance and angle, since spraying from too far away or at the wrong angle increases rebound, material that bounces off instead of bonding, and can leave hidden voids behind rebar, which is why ACI certifies nozzlemen specifically for this skill.
On a real project
A contractor building a swimming pool shell uses wet-mix shotcrete, sprayed by an ACI-certified nozzleman working around the pool's rebar cage from multiple angles to avoid trapping voids behind the steel.
Who this matters most to
A Concrete Worker or specialty shotcrete crew places it. A QA/QC Inspector checks for voids and rebound pockets, particularly behind congested rebar.
Where this goes wrong
An uncertified nozzleman sprays a retaining wall's rebar cage from too great a distance. Rebound material builds up behind the closely spaced bars instead of bonding solidly, leaving a hidden void that isn't discovered until a core sample taken during a later inspection reveals a soft spot.